EP2298697B1 - Method for producing a carbon wire assembly and a conductive film - Google Patents
Method for producing a carbon wire assembly and a conductive film Download PDFInfo
- Publication number
- EP2298697B1 EP2298697B1 EP09746538.9A EP09746538A EP2298697B1 EP 2298697 B1 EP2298697 B1 EP 2298697B1 EP 09746538 A EP09746538 A EP 09746538A EP 2298697 B1 EP2298697 B1 EP 2298697B1
- Authority
- EP
- European Patent Office
- Prior art keywords
- carbon
- wire
- film
- producing
- substrate
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
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- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 title claims description 627
- 229910052799 carbon Inorganic materials 0.000 title claims description 165
- 238000004519 manufacturing process Methods 0.000 title description 48
- 239000002041 carbon nanotube Substances 0.000 claims description 260
- 229910021393 carbon nanotube Inorganic materials 0.000 claims description 257
- 229910002804 graphite Inorganic materials 0.000 claims description 186
- 239000010439 graphite Substances 0.000 claims description 186
- 239000000758 substrate Substances 0.000 claims description 165
- 238000000034 method Methods 0.000 claims description 153
- 239000010410 layer Substances 0.000 claims description 90
- 239000007788 liquid Substances 0.000 claims description 84
- 229910003481 amorphous carbon Inorganic materials 0.000 claims description 71
- 229910052733 gallium Inorganic materials 0.000 claims description 63
- GYHNNYVSQQEPJS-UHFFFAOYSA-N Gallium Chemical compound [Ga] GYHNNYVSQQEPJS-UHFFFAOYSA-N 0.000 claims description 62
- 229920005989 resin Polymers 0.000 claims description 42
- 239000011347 resin Substances 0.000 claims description 42
- 229920001187 thermosetting polymer Polymers 0.000 claims description 11
- 230000001105 regulatory effect Effects 0.000 claims description 8
- 238000012546 transfer Methods 0.000 claims description 6
- 238000003466 welding Methods 0.000 claims description 6
- 239000002344 surface layer Substances 0.000 claims description 5
- 239000010408 film Substances 0.000 description 204
- 238000006243 chemical reaction Methods 0.000 description 100
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 68
- 239000010453 quartz Substances 0.000 description 65
- 230000000052 comparative effect Effects 0.000 description 34
- 239000007789 gas Substances 0.000 description 34
- 230000001965 increasing effect Effects 0.000 description 22
- YNPNZTXNASCQKK-UHFFFAOYSA-N phenanthrene Chemical compound C1=CC=C2C3=CC=CC=C3C=CC2=C1 YNPNZTXNASCQKK-UHFFFAOYSA-N 0.000 description 20
- 239000004215 Carbon black (E152) Substances 0.000 description 17
- PNEYBMLMFCGWSK-UHFFFAOYSA-N aluminium oxide Inorganic materials [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 description 17
- 229930195733 hydrocarbon Natural products 0.000 description 17
- 150000002430 hydrocarbons Chemical class 0.000 description 17
- 229910021389 graphene Inorganic materials 0.000 description 15
- 238000010438 heat treatment Methods 0.000 description 15
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- 239000003054 catalyst Substances 0.000 description 12
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- CSCPPACGZOOCGX-UHFFFAOYSA-N Acetone Chemical compound CC(C)=O CSCPPACGZOOCGX-UHFFFAOYSA-N 0.000 description 10
- BBEAQIROQSPTKN-UHFFFAOYSA-N pyrene Chemical compound C1=CC=C2C=CC3=CC=CC4=CC=C1C2=C43 BBEAQIROQSPTKN-UHFFFAOYSA-N 0.000 description 10
- 238000005259 measurement Methods 0.000 description 9
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 description 7
- PXHVJJICTQNCMI-UHFFFAOYSA-N nickel Substances [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 description 7
- 229910052710 silicon Inorganic materials 0.000 description 7
- 239000010703 silicon Substances 0.000 description 7
- 239000002356 single layer Substances 0.000 description 7
- 239000002002 slurry Substances 0.000 description 7
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 description 6
- VEXZGXHMUGYJMC-UHFFFAOYSA-N Hydrochloric acid Chemical compound Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 description 5
- 238000000429 assembly Methods 0.000 description 5
- 230000000712 assembly Effects 0.000 description 5
- 239000002775 capsule Substances 0.000 description 5
- 125000002837 carbocyclic group Chemical group 0.000 description 5
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- 238000000576 coating method Methods 0.000 description 5
- GVEPBJHOBDJJJI-UHFFFAOYSA-N fluoranthrene Natural products C1=CC(C2=CC=CC=C22)=C3C2=CC=CC3=C1 GVEPBJHOBDJJJI-UHFFFAOYSA-N 0.000 description 5
- 238000005087 graphitization Methods 0.000 description 5
- 239000002105 nanoparticle Substances 0.000 description 5
- 239000002109 single walled nanotube Substances 0.000 description 5
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 description 4
- 238000005299 abrasion Methods 0.000 description 4
- 239000010949 copper Substances 0.000 description 4
- 238000010586 diagram Methods 0.000 description 4
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- XEEYBQQBJWHFJM-UHFFFAOYSA-N iron Substances [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 4
- 229910052759 nickel Inorganic materials 0.000 description 4
- 238000004528 spin coating Methods 0.000 description 4
- 239000010409 thin film Substances 0.000 description 4
- 238000007740 vapor deposition Methods 0.000 description 4
- DSSYKIVIOFKYAU-XCBNKYQSSA-N (R)-camphor Chemical compound C1C[C@@]2(C)C(=O)C[C@@H]1C2(C)C DSSYKIVIOFKYAU-XCBNKYQSSA-N 0.000 description 3
- 241000723346 Cinnamomum camphora Species 0.000 description 3
- SXFQCTMHFJARRW-UHFFFAOYSA-N acetylene;methane Chemical group C.C#C SXFQCTMHFJARRW-UHFFFAOYSA-N 0.000 description 3
- -1 alum Chemical compound 0.000 description 3
- 229910052786 argon Inorganic materials 0.000 description 3
- 229960000846 camphor Drugs 0.000 description 3
- 229930008380 camphor Natural products 0.000 description 3
- 229910052802 copper Inorganic materials 0.000 description 3
- 238000000151 deposition Methods 0.000 description 3
- 230000008021 deposition Effects 0.000 description 3
- 238000010894 electron beam technology Methods 0.000 description 3
- 239000011521 glass Substances 0.000 description 3
- 239000012535 impurity Substances 0.000 description 3
- 238000010884 ion-beam technique Methods 0.000 description 3
- 229910052742 iron Inorganic materials 0.000 description 3
- 239000002048 multi walled nanotube Substances 0.000 description 3
- 238000012545 processing Methods 0.000 description 3
- VTYYLEPIZMXCLO-UHFFFAOYSA-L Calcium carbonate Chemical compound [Ca+2].[O-]C([O-])=O VTYYLEPIZMXCLO-UHFFFAOYSA-L 0.000 description 2
- CSNNHWWHGAXBCP-UHFFFAOYSA-L Magnesium sulfate Chemical compound [Mg+2].[O-][S+2]([O-])([O-])[O-] CSNNHWWHGAXBCP-UHFFFAOYSA-L 0.000 description 2
- 125000004429 atom Chemical group 0.000 description 2
- OSGAYBCDTDRGGQ-UHFFFAOYSA-L calcium sulfate Chemical compound [Ca+2].[O-]S([O-])(=O)=O OSGAYBCDTDRGGQ-UHFFFAOYSA-L 0.000 description 2
- 150000001721 carbon Chemical group 0.000 description 2
- 239000003575 carbonaceous material Substances 0.000 description 2
- 239000011651 chromium Substances 0.000 description 2
- 239000000470 constituent Substances 0.000 description 2
- 239000013078 crystal Substances 0.000 description 2
- 238000007766 curtain coating Methods 0.000 description 2
- 230000003247 decreasing effect Effects 0.000 description 2
- 229910003460 diamond Inorganic materials 0.000 description 2
- 239000010432 diamond Substances 0.000 description 2
- 238000003618 dip coating Methods 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 238000001704 evaporation Methods 0.000 description 2
- 230000002209 hydrophobic effect Effects 0.000 description 2
- 239000011572 manganese Substances 0.000 description 2
- 229910052751 metal Inorganic materials 0.000 description 2
- 239000002184 metal Substances 0.000 description 2
- 239000010445 mica Substances 0.000 description 2
- 229910052618 mica group Inorganic materials 0.000 description 2
- 229910003465 moissanite Inorganic materials 0.000 description 2
- 239000004065 semiconductor Substances 0.000 description 2
- 229910010271 silicon carbide Inorganic materials 0.000 description 2
- 239000000243 solution Substances 0.000 description 2
- 238000005507 spraying Methods 0.000 description 2
- 239000012780 transparent material Substances 0.000 description 2
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 2
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 1
- VYZAMTAEIAYCRO-UHFFFAOYSA-N Chromium Chemical compound [Cr] VYZAMTAEIAYCRO-UHFFFAOYSA-N 0.000 description 1
- 230000005355 Hall effect Effects 0.000 description 1
- PWHULOQIROXLJO-UHFFFAOYSA-N Manganese Chemical compound [Mn] PWHULOQIROXLJO-UHFFFAOYSA-N 0.000 description 1
- GRYLNZFGIOXLOG-UHFFFAOYSA-N Nitric acid Chemical compound O[N+]([O-])=O GRYLNZFGIOXLOG-UHFFFAOYSA-N 0.000 description 1
- NIXOWILDQLNWCW-UHFFFAOYSA-N acrylic acid group Chemical group C(C=C)(=O)O NIXOWILDQLNWCW-UHFFFAOYSA-N 0.000 description 1
- 238000004220 aggregation Methods 0.000 description 1
- 230000002776 aggregation Effects 0.000 description 1
- 150000004996 alkyl benzenes Chemical group 0.000 description 1
- 229940037003 alum Drugs 0.000 description 1
- 229910052782 aluminium Inorganic materials 0.000 description 1
- ILRRQNADMUWWFW-UHFFFAOYSA-K aluminium phosphate Chemical compound O1[Al]2OP1(=O)O2 ILRRQNADMUWWFW-UHFFFAOYSA-K 0.000 description 1
- ANBBXQWFNXMHLD-UHFFFAOYSA-N aluminum;sodium;oxygen(2-) Chemical compound [O-2].[O-2].[Na+].[Al+3] ANBBXQWFNXMHLD-UHFFFAOYSA-N 0.000 description 1
- 238000000137 annealing Methods 0.000 description 1
- 229910052586 apatite Inorganic materials 0.000 description 1
- 229940077388 benzenesulfonate Drugs 0.000 description 1
- 230000005540 biological transmission Effects 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 229910000019 calcium carbonate Inorganic materials 0.000 description 1
- 229940043430 calcium compound Drugs 0.000 description 1
- 150000001674 calcium compounds Chemical class 0.000 description 1
- BRPQOXSCLDDYGP-UHFFFAOYSA-N calcium oxide Chemical compound [O-2].[Ca+2] BRPQOXSCLDDYGP-UHFFFAOYSA-N 0.000 description 1
- 239000000292 calcium oxide Substances 0.000 description 1
- ODINCKMPIJJUCX-UHFFFAOYSA-N calcium oxide Inorganic materials [Ca]=O ODINCKMPIJJUCX-UHFFFAOYSA-N 0.000 description 1
- 239000001506 calcium phosphate Substances 0.000 description 1
- 229910000389 calcium phosphate Inorganic materials 0.000 description 1
- 235000011010 calcium phosphates Nutrition 0.000 description 1
- 239000000919 ceramic Substances 0.000 description 1
- 238000005229 chemical vapour deposition Methods 0.000 description 1
- 229910052804 chromium Inorganic materials 0.000 description 1
- 229910017052 cobalt Inorganic materials 0.000 description 1
- 239000010941 cobalt Substances 0.000 description 1
- GUTLYIVDDKVIGB-UHFFFAOYSA-N cobalt atom Chemical compound [Co] GUTLYIVDDKVIGB-UHFFFAOYSA-N 0.000 description 1
- 239000004020 conductor Substances 0.000 description 1
- 230000001276 controlling effect Effects 0.000 description 1
- 238000007796 conventional method Methods 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 229910001873 dinitrogen Inorganic materials 0.000 description 1
- 239000006185 dispersion Substances 0.000 description 1
- 239000002612 dispersion medium Substances 0.000 description 1
- 230000005611 electricity Effects 0.000 description 1
- 239000003822 epoxy resin Substances 0.000 description 1
- 239000010419 fine particle Substances 0.000 description 1
- 238000004050 hot filament vapor deposition Methods 0.000 description 1
- 230000001939 inductive effect Effects 0.000 description 1
- 238000009776 industrial production Methods 0.000 description 1
- 239000011261 inert gas Substances 0.000 description 1
- 239000012212 insulator Substances 0.000 description 1
- 230000010354 integration Effects 0.000 description 1
- 238000005304 joining Methods 0.000 description 1
- 239000004973 liquid crystal related substance Substances 0.000 description 1
- 150000002681 magnesium compounds Chemical class 0.000 description 1
- VTHJTEIRLNZDEV-UHFFFAOYSA-L magnesium dihydroxide Chemical compound [OH-].[OH-].[Mg+2] VTHJTEIRLNZDEV-UHFFFAOYSA-L 0.000 description 1
- 239000000347 magnesium hydroxide Substances 0.000 description 1
- 229910001862 magnesium hydroxide Inorganic materials 0.000 description 1
- 239000000395 magnesium oxide Substances 0.000 description 1
- CPLXHLVBOLITMK-UHFFFAOYSA-N magnesium oxide Inorganic materials [Mg]=O CPLXHLVBOLITMK-UHFFFAOYSA-N 0.000 description 1
- GVALZJMUIHGIMD-UHFFFAOYSA-H magnesium phosphate Chemical compound [Mg+2].[Mg+2].[Mg+2].[O-]P([O-])([O-])=O.[O-]P([O-])([O-])=O GVALZJMUIHGIMD-UHFFFAOYSA-H 0.000 description 1
- 239000004137 magnesium phosphate Substances 0.000 description 1
- 229910000157 magnesium phosphate Inorganic materials 0.000 description 1
- 229960002261 magnesium phosphate Drugs 0.000 description 1
- 235000010994 magnesium phosphates Nutrition 0.000 description 1
- 229910052943 magnesium sulfate Inorganic materials 0.000 description 1
- 235000019341 magnesium sulphate Nutrition 0.000 description 1
- AXZKOIWUVFPNLO-UHFFFAOYSA-N magnesium;oxygen(2-) Chemical compound [O-2].[Mg+2] AXZKOIWUVFPNLO-UHFFFAOYSA-N 0.000 description 1
- 229910052748 manganese Inorganic materials 0.000 description 1
- 239000013081 microcrystal Substances 0.000 description 1
- 239000000203 mixture Substances 0.000 description 1
- 229910052750 molybdenum Inorganic materials 0.000 description 1
- 239000002071 nanotube Substances 0.000 description 1
- 229910017604 nitric acid Inorganic materials 0.000 description 1
- 230000003287 optical effect Effects 0.000 description 1
- 239000002245 particle Substances 0.000 description 1
- VSIIXMUUUJUKCM-UHFFFAOYSA-D pentacalcium;fluoride;triphosphate Chemical compound [F-].[Ca+2].[Ca+2].[Ca+2].[Ca+2].[Ca+2].[O-]P([O-])([O-])=O.[O-]P([O-])([O-])=O.[O-]P([O-])([O-])=O VSIIXMUUUJUKCM-UHFFFAOYSA-D 0.000 description 1
- 238000010587 phase diagram Methods 0.000 description 1
- 229910052697 platinum Inorganic materials 0.000 description 1
- 229920000647 polyepoxide Polymers 0.000 description 1
- 239000000377 silicon dioxide Substances 0.000 description 1
- 229910052814 silicon oxide Inorganic materials 0.000 description 1
- 229910001388 sodium aluminate Inorganic materials 0.000 description 1
- 239000006104 solid solution Substances 0.000 description 1
- 239000002904 solvent Substances 0.000 description 1
- 229910001220 stainless steel Inorganic materials 0.000 description 1
- 239000010935 stainless steel Substances 0.000 description 1
- 239000004094 surface-active agent Substances 0.000 description 1
- 230000002194 synthesizing effect Effects 0.000 description 1
- 239000006188 syrup Substances 0.000 description 1
- 235000020357 syrup Nutrition 0.000 description 1
- JBQYATWDVHIOAR-UHFFFAOYSA-N tellanylidenegermanium Chemical compound [Te]=[Ge] JBQYATWDVHIOAR-UHFFFAOYSA-N 0.000 description 1
- 238000002834 transmittance Methods 0.000 description 1
- QORWJWZARLRLPR-UHFFFAOYSA-H tricalcium bis(phosphate) Chemical compound [Ca+2].[Ca+2].[Ca+2].[O-]P([O-])([O-])=O.[O-]P([O-])([O-])=O QORWJWZARLRLPR-UHFFFAOYSA-H 0.000 description 1
- LEONUFNNVUYDNQ-UHFFFAOYSA-N vanadium atom Chemical compound [V] LEONUFNNVUYDNQ-UHFFFAOYSA-N 0.000 description 1
Images
Classifications
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- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
- C01B32/00—Carbon; Compounds thereof
- C01B32/15—Nano-sized carbon materials
- C01B32/158—Carbon nanotubes
- C01B32/16—Preparation
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B82—NANOTECHNOLOGY
- B82Y—SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
- B82Y10/00—Nanotechnology for information processing, storage or transmission, e.g. quantum computing or single electron logic
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B82—NANOTECHNOLOGY
- B82Y—SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
- B82Y30/00—Nanotechnology for materials or surface science, e.g. nanocomposites
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B82—NANOTECHNOLOGY
- B82Y—SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
- B82Y40/00—Manufacture or treatment of nanostructures
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01B—CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
- H01B1/00—Conductors or conductive bodies characterised by the conductive materials; Selection of materials as conductors
- H01B1/04—Conductors or conductive bodies characterised by the conductive materials; Selection of materials as conductors mainly consisting of carbon-silicon compounds, carbon or silicon
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01B—CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
- H01B1/00—Conductors or conductive bodies characterised by the conductive materials; Selection of materials as conductors
- H01B1/20—Conductive material dispersed in non-conductive organic material
- H01B1/24—Conductive material dispersed in non-conductive organic material the conductive material comprising carbon-silicon compounds, carbon or silicon
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01B—CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
- H01B13/00—Apparatus or processes specially adapted for manufacturing conductors or cables
- H01B13/0036—Details
-
- H—ELECTRICITY
- H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10K—ORGANIC ELECTRIC SOLID-STATE DEVICES
- H10K30/00—Organic devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation
- H10K30/80—Constructional details
- H10K30/81—Electrodes
- H10K30/82—Transparent electrodes, e.g. indium tin oxide [ITO] electrodes
- H10K30/821—Transparent electrodes, e.g. indium tin oxide [ITO] electrodes comprising carbon nanotubes
-
- H—ELECTRICITY
- H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10K—ORGANIC ELECTRIC SOLID-STATE DEVICES
- H10K71/00—Manufacture or treatment specially adapted for the organic devices covered by this subclass
- H10K71/60—Forming conductive regions or layers, e.g. electrodes
-
- H—ELECTRICITY
- H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10K—ORGANIC ELECTRIC SOLID-STATE DEVICES
- H10K85/00—Organic materials used in the body or electrodes of devices covered by this subclass
- H10K85/20—Carbon compounds, e.g. carbon nanotubes or fullerenes
- H10K85/221—Carbon nanotubes
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
- C01B2202/00—Structure or properties of carbon nanotubes
- C01B2202/20—Nanotubes characterized by their properties
- C01B2202/34—Length
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
- C01B2202/00—Structure or properties of carbon nanotubes
- C01B2202/20—Nanotubes characterized by their properties
- C01B2202/36—Diameter
-
- H—ELECTRICITY
- H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10K—ORGANIC ELECTRIC SOLID-STATE DEVICES
- H10K10/00—Organic devices specially adapted for rectifying, amplifying, oscillating or switching; Organic capacitors or resistors having potential barriers
- H10K10/80—Constructional details
- H10K10/82—Electrodes
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- H—ELECTRICITY
- H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10K—ORGANIC ELECTRIC SOLID-STATE DEVICES
- H10K50/00—Organic light-emitting devices
- H10K50/80—Constructional details
- H10K50/805—Electrodes
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E10/00—Energy generation through renewable energy sources
- Y02E10/50—Photovoltaic [PV] energy
- Y02E10/549—Organic PV cells
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P70/00—Climate change mitigation technologies in the production process for final industrial or consumer products
- Y02P70/50—Manufacturing or production processes characterised by the final manufactured product
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
- Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y10S977/00—Nanotechnology
- Y10S977/84—Manufacture, treatment, or detection of nanostructure
- Y10S977/89—Deposition of materials, e.g. coating, cvd, or ald
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
- Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y10S977/00—Nanotechnology
- Y10S977/902—Specified use of nanostructure
- Y10S977/932—Specified use of nanostructure for electronic or optoelectronic application
Definitions
- the present invention relates generally to carbon wires, wire assemblies and methods of producing the same, and particularly to carbon wires, wire assemblies and methods of producing the same, that employ a plurality of carbon filaments.
- the present invention also relates to electrically conductive film, electrically conductive substrates, and transparent, electrically conductive sheet including graphite film, that are obtained by exposing a carbon nanotube network to Ga vapor, and methods of producing the same.
- the present invention also relates to methods of obtaining graphite film by exposing a carbon source to Ga vapor.
- a carbon nanotube As one example of a carbon filament, a carbon nanotube (CNT) has excellent properties and is accordingly expected to be employed in a variety of industrial applications.
- a CNT provides substantially as low an electrical resistance value as copper and is thus considered to be used as a material for wire.
- such CNT is produced in a variety of methods, as proposed for example in Japanese Patent Laying-Open No. 2007-112662 (Patent Document 1).
- Japanese Patent Laying-Open No. 2007-112662 proposes a method in which a metal catalyst of gallium (Ga) is introduced in an amorphous carbon wire structure and a direct current is applied thereto to produce a CNT sized, shaped and oriented as desired.
- Ga gallium
- graphene When a carbon atom is chemically bonded by an sp2 hybridized orbital, it forms a lattice-structured film having two dimensionally spread carbocyclic six-membered rings packed in a plane. This carbon atom's two dimensional planar structure is referred to as graphene.
- graphene in a tubular closed structure is a carbon nanotube, and graphene layers stacked in a direction of a normal thereto are graphite.
- a carbon nanotube is a tabular material having a diameter equal to or smaller than 1 ⁇ m, and ideally, a film in a lattice structure of carbocyclic six-membered rings has planes parallel to a tube's axis to form the tube, and a multiple of such tubes may be provided.
- the carbon nanotube is theoretically expected to exhibit a metallic property or a semiconducting property depending on how the lattice structured films have carbocyclic six-membered rings linked and the tube's thickness, and it is thus expected as a future high-porformance material.
- Patent Document 2 discloses organizing carbon nanotubes to provide a structure by dispersing carbon nanotubes in a dispersion medium for example ultrasonically to prepare a dispersion liquid of carbon nanotubes which is in turn dropped on a planar substrate and dried thereon to provide a thin film of carbon nanotubes.
- the thin film of carbon nanotubes has the carbon nanotubes interconnected simply by contacting one another, and is thus disadvantageously high in contact resistance.
- Graphite has a variety of electrical properties, as observed on graphite film, such as a bandgap, a fractional quantum Hall effect and the like varying with in what size it is cut out, and is thus gaining a large attention in recent years not only for physical phenomena but also in terms of application to devices in the future.
- Non Patent Document 1 K. S, Novoselov et. al., Science 306 (2004) pp. 666-669 .
- Non Patent Document 2 K. S. Novoselov et. al., Proc. Natl. Acad. Sci. U.S.A, 102 (2005) pp. 10451-10453 .
- Non Patent Document 2 C. Berger et. al., J. Phys. Chem. B108 (2004) pp. 19912-19916 .
- Non Patent Document 3 Yuanbo Zhang et. al., Nature 438, pp. 201-204 (10 November, 2005 )
- Non Patent Document 4 disclose techniques used to produce a monolayer of graphite film, i.e., graphene.
- Non Patent Document 1 K.S. Novoselov et. al., Science 306 (2004) pp. 666-669
- Non Patent Document 2 K.S. Novoselov et. al., Proc. Natl. Acad. Sci. U.S.A 102 (2005) pp. 10451-10453 .
- Non Patent Document 2 More specifically, Scotch tape is stuck on graphite crystal to peel off graphite to leave a single sheet of graphene on a silicon substrate having a surface oxidized and a monolayer of graphene is found and utilized. This technique is a rather primitive technique.
- Non Patent Document 3 discloses that a high temperature process at 1400-1600°C is performed in an environment of ultrahigh vacuum to decompose a SiC monocrystalline surface and after Si is selectively sublimated a monolayer of graphene is synthesized. Furthermore, it is also disclosed that a diamond microcrystal is first formed and then processed at 1600°C to obtain graphene from diamond.
- Non Patent Document 4 discloses a method employing chemical vapor deposition to produce graphene. More specifically, camphor vapor is thermally decomposed at 700-850°C at an Ni crystal face to obtain graphene.
- US2007/284557 A1 relates to a graphene film as a transparent and electrically conducting material.
- WO 2008/051302 A1 relates to end-to-end joining of nanotubes.
- JP 2007115903 A relates to a semiconductor device and its manufacturing method.
- the present invention has been made to overcome such disadvantage as described above, and it contemplates a carbon wire employing CNT or a similar carbon filament having a sufficiently low electrical resistance value, and a wire assembly employing the carbon wire.
- the present invention also contemplates electrically conductive film having a carbon nanotube network formed of a plurality of low resistance carbon nanotubes linked together by graphite film, an electrically conductive substrate and a transparent, electrically conductive sheet employing the same, and a method for reproducibly producing the same.
- the present invention also contemplates a method of producing graphite film that can facilitate synthesizing a large area of graphite film significantly reproducibly.
- a carbon wire includes an assembly portion and a graphite layer.
- the assembly portion is formed of a plurality of carbon filaments in contact with one another.
- the graphite layer is provided at an outer circumference of the assembly portion.
- the carbon wire can have an outer circumferential graphite layer holding an assembly portion to ensure that the assembly portion has its carbon filaments in contact with one another. This allows the assembly portion to have the carbon filaments in contact with one another over an increased area with increased pressure exerted to that area. This can prevent the assembly portion from having the carbon filaments in contact with one another insufficiently and the carbon wire from accordingly having an increased electrical resistance value.
- the graphite layer can also act as an electrically conductive layer to allow the carbon wire to have a further reduced electrical resistance value.
- the carbon filament may be a carbon nanotube.
- the carbon wire can have a further reduced electrical resistance value.
- the graphite layer may be a carbon nanotube.
- the graphite layer can also act as an electrically conductive layer, and can thus more effectively reduce the carbon wire's electrical resistance.
- a wire assembly includes a plurality of the above carbon wires. This allows the wire assembly to be sufficiently low in resistance. Furthermore, the plurality of carbon wires assembly to have a large area in cross section and accordingly enable the wire assembly to pass a current of a large value.
- a method of producing a carbon wire includes the steps of: preparing an assembly portion formed of a plurality of carbon filaments in contact with one another, and exposing a surface of the assembly portion to liquid gallium to provide a graphite layer on the surface of the assembly portion.
- the step of exposing may be performed with compressive stress exerted to the assembly portion.
- the step of exposing may be performed with liquid gallium compressed to exert compressive stress to the assembly portion.
- the liquid gallium compressed (for example by increasing the pressure of an ambient gas that is brought into contact with the liquid gallium, or by enclosing Ga and CNTs in a capsule or a similar container and then compressing them together with the capsule (or container) can facilitate exerting compressive stress to the assembly portion.
- the step of exposing may be performed with the liquid gallium in contact with ambient gas regulated in pressure to compress the liquid gallium, This can facilitate compressing the liquid gallium. Furthermore, regulating the ambient gas's pressure can facilitate regulating the value of the pressure applied to the liquid gallium,
- the step of exposing is performed with the liquid gallium having a temperature in a range of 450°C-750°C. This can more efficiently cause the liquid gallium's catalytic reaction providing the graphite layer from an outer circumference of the assembly portion.
- the liquid gallium's lower temperature limit is set at 450°C because if the liquid gallium has a temperature lower than that temperature, the liquid gallium's catalytic reaction is insufficiently provided.
- the liquid gallium's upper temperature limit is set at 750°C in order to prevent the assembly portion from having its constituent carbon filaments decomposed.
- the above method of producing a carbon wire may include, before the step of exposing, the step of providing an amorphous carbon layer as a surface layer of the assembly portion.
- Previously providing the amorphous carbon layer that is to serve as the graphite layer allows the graphite layer to be provided while in the assembly portion the carbon filaments' structure can be maintained. This allows an increased degree of freedom in designing the carbon wire in configuration.
- the above method of producing a carbon wire may further include, after the step of exposing, the step of removing gallium adhering to a surface of the carbon wire.
- the step of exposing may results in the carbon wire having a surface with the liquid gallium solidified and thus adhering thereto.
- the step of removing can remove such solidified gallium from the surface of the carbon wire.
- a method of producing a wire assembly includes the step of: producing a plurality of carbon wires in the above method of producing carbon wire; and stranding the plurality of carbon wire together to form a wire assembly.
- Low-resistance carbon wires according to the present invention can thus be used to produce a wire assembly.
- a reference example provides electrically conductive film having a carbon nanotube network formed of a plurality of carbon nanotubes linked together by graphite film.
- the present invention provides a method of producing the electrically conductive film having a carbon nanotube network formed of a plurality of carbon nanotubes linked together by graphite film, including the step of exposing a carbon nanotube network to Ga vapor to provide the graphite film.
- Bulk Ga and carbon as seen in phase diagram are of a non solid solution type.
- the present inventors have found that in a microscale, Ga and carbon at their surfaces have a bond caused and Ga vapor per se has a catalysis for graphitization reaction.
- the present invention provides a method of producing the electrically conductive film according to claim 10.
- the present inventors have found that Ga not only in the form of an aggregation of atoms as liquid but also in the form of vapor having atoms liberated converts to a graphite structure at a surface of amorphous carbon, i.e., that it causes a graphitization reaction of the surface of amorphous carbon.
- the present invention includes the step of causing Ga vapor to act on amorphous carbon or a similar carbon source to graphitize its surface.
- graphite film includes both a graphene film in the form of a single layer, and a graphite film formed of graphene films stacked in a plurality of layers.
- the method of producing the electrically conductive film preferably includes, before the step of exposing, the step of mechanically pressure-welding those portions of a plurality of carbon nanotubes forming the carbon nanotube network which are in contact with one another.
- a reference example provides an electrically conductive substrate formed with a substrate and electrically conductive film provided on the substrate and having a carbon nanotube network formed of a plurality of carbon nanotubes linked together by graphite film.
- the present invention provides a method of producing an electrically conductive substrate, according to claim 12.
- the present invention provides a method of producing the electrically conductive substrate according to claim 13.
- the method of producing the electrically conductive substrate preferably includes, before the step of exposing, the step of mechanically pressure-welding those portions of a plurality of carbon nanotubes forming the carbon nanotube network which are in contact with one another.
- a reference example provides a transparent, electrically conductive sheet formed with a sheet of resin and electrically conductive film provided on the sheet of resin and having a carbon nanotube network formed of a plurality of carbon nanotubes linked together by graphite film.
- a surface of the sheet of resin that has the electrically conductive film is formed of one of thermosetting resin and ultraviolet (UV) curable resin.
- the present invention provides a method of producing the transparent, electrically conductive sheet according to claim 15.
- the present invention provides a method of producing the transparent, electrically conductive sheet according to claim 16.
- the method of producing a transparent, electrically conductive sheet preferably includes, before the step of exposing, the step of mechanically pressure-welding those portions of the plurality of carbon nanotubes forming the carbon nanotube network which are in contact with one another.
- the method of producing a transparent, electrically conductive sheet includes the step of transferring to transfer the electrically conductive film to the surface of the sheet of resin that is formed of one of thermosetting resin and ultraviolet curable resin, and the method further includes the step of setting/curing one of the thermosetting resin and the ultraviolet curable resin.
- a reference example provides a method of producing graphite film by exposing a surface of a carbon source to Ga vapor to provide graphite film on the surface of the carbon source.
- the Ga vapor has a temperature equal to or higher than 600°C.
- Ga vapor having a temperature of 600°C or higher allows graphitization reaction to proceed satisfactorily.
- the Ga vapor has a uniform vapor pressure at the surface of the carbon source. This allows a graphite film to be provided with a homogenous property.
- the Ga vapor is plasmatized.
- the carbon source is located on a substrate and the Ga vapor plasmatized is brought into contact with the substrate having a temperature equal to or higher than 400°C.
- Ga vapor plasmatized allows graphite film to be provided while the substrate having a source material of amorphous carbon applied thereon is maintained at as low a temperature as approximately 400°C.
- Semiconductor device processes require significantly strict temperature restrictions in order to maintain impurity profiles of channels, source/drain layers and the like. For example, approximately 500°C or higher temperatures cannot be set for processing. Plasmatized gallium allows catalysis to be exhibited at a temperature equal to or lower than 400°C.
- the carbon source is amorphous carbon.
- the amorphous carbon is amorphous carbon film provided on a monocrystalline substrate formed of one type selected from the group consisting of SiC. Ni, Fe, Mo, and Pt.
- the graphite film when a graphite film is provided on a silicon oxide film, the graphite film is not necessarily provided as monocrystalline film and instead as polycrystalline film having a domain structure in a broad sense.
- An underlying substrate that is a SiC, Ni, Fe, Mo, Pt or similar crystalline substrate allows graphite film to be provided as monocrystalline film.
- the carbon source is a hydrocarbon material.
- the carbon source other than amorphous carbon may be used, such as phenanthrene, pyrene, camphor or similar hydrocarbon materials.
- the carbon source can be a three dimensional amorphous carbon structure having a surface exposed to Ga vapor to provide graphite film having a three dimensional surface structure.
- Ga vapor used as a catalyst can graphitize not only amorphous carbon in the form of a plane but also a surface of a pillar or a similar, three dimensional, any spatial geometry of amorphous carbon.
- a reference example relates to a method of producing graphite film by mixing Ga vapor and a source material gas of a carbon source together and supplying a mixture thereof to provide graphite film on a substrate. This allows the substrate to have relatively thick graphite film thereon.
- the Ga vapor has a temperature equal to or higher than 600°C or higher.
- the Ga vapor is plasmatized.
- the Ga vapor plasmatized is brought into contact with the substrate having a temperature equal to or higher than 400°C.
- the present invention can achieve a low resistance carbon wire and a low resistance wire assembly.
- the present invention can achieve a low resistance electrically conductive film having a carbon nanotube network, and an electrically conductive substrate and a transparent, electrically conductive sheet utilizing the same;
- the present invention also has a side effect including large light transmission. If fine particles or the like are used to provide a surface of a substrate with electrical conductivity, the particles must be closely packed to cover the surface of the substrate entirely. In contrast, carbon nanotubes can eliminate the necessity of covering the surface of the substrate entirely. The carbon nanotubes that do not entirely cover the surface of the substrate allow the substrate to have the surface with many gaps, which can facilitate transmitting light.
- the present method of producing graphite film is applicable to producing a transparent, electrically conductive sheet used for a variety of electronic devices, large-size displays and the like.
- the present invention for device applications, can facilitate efficient mass production of monocrystalline graphite film.
- the present invention, for transparent, electrically conductive sheet can provide means for obtaining a large area and number of layers of graphite film
- Fig. 1 is a schematic cross section showing an embodiment of a carbon wire in the present invention.
- Fig. 2 is a schematic cross section taken along a line II-II shown in Fig. 1 .
- the present invention provides a carbon wire 1, as will be described hereinafter. Note that Fig. 1 shows carbon wire 1 in cross section as seen in a direction perpendicular to its longitudinal direction and Fig. 2 shows carbon wire 1 in cross section as seen in a direction along its longitudinal direction.
- carbon wire 1 includes an assembly portion 3 and a graphite layer 4.
- Assembly portion 3 is configured of a plurality of carbon filaments implemented as carbon nanotubes 2 in contact with one another.
- Graphite layer 4 surrounds assembly portion 3.
- Fig. 1 and Fig. 2 show carbon wire 1 configured, as seen in cross section, of two carbon nanotubes 2
- carbon wire 1 may have assembly portion 3 configured, as seen in cross section, of two or more, e.g., three or four carbon nanotubes (CNTs) 2.
- assembly portion 3 is configured of carbon nanotubes 2 in contact with one another.
- Fig. 1 and Fig. 2 assembly portion 3 is configured of carbon nanotubes 2 in contact with one another.
- carbon wire 1 as seen in its longitudinal direction also has carbon nanotubes 2 successively in contact with one another to allow assembly portion 3 to have carbon nanotubes 2 forming an electrically conducting path extending in the longitudinal direction of carbon wire 1 and capable of passing an electric current therethrough.
- Carbon wire 1 can thus have an outer circumference formed of graphite layer 4. holding assembly portion 3 to ensure that assembly portion 3 has carbon nanotubes 2 in contact with one another. This allows assembly portion 3 to have carbon nanotubes 2 in contact with one another over an increased area with increased pressure exerted to that area. This can prevent assembly portion 3 from having carbon nanotubes 2 in contact with one another insufficiently and hence carbon wire 1 from having an increased electrical resistance value. Furthermore, graphite layer 4 can also act as an electrically conductive layer allowing carbon wire 1 to have a further reduced electrical resistance value.
- carbon wire 1 including assembly portion 3 configured of carbon filaments formed of satisfactorily electrically conductive carbon nanotubes 2 ensures that carbon wire 1 has a reduced electrical resistance value.
- carbon wire 1 has graphite layer 4 formed of a carbon nanotube.
- graphite layer 4 can also act as an electrically conductive layer, and carbon wire 1 can further be reduced in electrical resistance.
- graphite layer 4 causes carbon nanotubes 2 that configure assembly portion 3 to press one another. This allows assembly portion 3 to have carbon nanotubes 2 in contact with one another over an increased area with increased pressure exerted to that area, and also allows graphite layer 4 to contact carbon nanotubes 2 of assembly portion 3 over an increased area with increased pressure exerted to that area. As a result, carbon wire 1 of low resistance can be implemented.
- Fig. 3 is a schematic cross section showing an embodiment of a wire assembly in the present invention.
- the present invention provides a wire assembly 5, as will be described hereinafter.
- Fig. 3 shows wire assembly 5 in cross section as seen in a direction perpendicular to its longitudinal direction.
- wire assembly 5 includes a plurality of carbon wires 1 as described above (in Fig. 3 , it includes seven carbon wires 1).
- carbon wire 1 of low resistance produced according to the method of the present invention can be used to implement wire assembly 5 of sufficiently low resistance.
- using a plurality of carbon wires 1 allows wire assembly 5 to have a large area in cross section and hence pass a current having a large value.
- wire assembly 5 may have a plurality of carbon wires 1 twined together, or simply bundied and bound by a clamping member surrounding the plurality of carbon wires 1.
- the clamping member may for example be an annular clamp formed for example of insulator (e.g., resin).
- wire assembly 5 may be configured of carbon wires 1 different in number than as shown in Fig. 3 (for example, the wire assembly may be configured of two or any larger number of carbon wires).
- Fig. 3 shows wire assembly 5 configured of carbon wires 1 all identically structured, carbon wire 1 may be different in configuration for some portion in cross section of wire assembly 5.
- wire assembly 5 as seen in cross section may have a center portion with carbon wire 1 configured of carbon nanotubes 2 (see Fig.
- wire assembly 5 as seen in cross section may have an outer circumference with carbon wire 1 configured of carbon nanotubes 2 bundled in a number smaller than that of carbon nanotubes 2 bundled that are located in carbon wire 1 at the center portion (e.g., less than ten, more specifically, five or less carbon nanotubes 2 may be bundled together).
- wire assembly 5 may be exposed to liquid gallium (a Ga catalyst), as done in the step of providing graphite layer 4 for carbon wire 1, as will be described hereinafter, to provide a graphite layer surrounding wire assembly 5. Furthermore, a plurality of wire assemblies 5 each externally circumferentially surrounded by the graphite layer are prepared and bundled together to prepare a wire having a larger area in cross section. Furthermore, the wire is also exposed to liquid gallium to have a graphite layer surrounding the wire. Furthermore, a plurality of such wires each externally circumferentially surrounded by the graphite layer are bundled together to configure a wire having a larger area in cross section.
- liquid gallium a Ga catalyst
- Fig. 4 is a flowchart for illustrating a method of producing the Fig. 3 wire assembly.
- the Fig. 3 wire assembly is produced in the method, as will be described hereinafter.
- wire assembly 5 is produced in a method in which a CNT production step (S10) is first performed.
- a CNT production step (S10) a short (e.g., several ⁇ m long) carbon nanotube is production in a conventionally well known method.
- a substrate used to produce a CNT is provided on a surface thereof with an underlying film, and on the underlying film a plurality of nanoparticles acting as a catalyst for forming a carbon nanotube are formed such that they are dispersed.
- the underlying, film is configured of material preferably for example of alumina, silica, sodium aluminate, alum, aluminum phosphate or a similar aluminum compound, calcium oxide, calcium carbonate, calcium sulfate or a similar calcium compound, magnesium oxide, magnesium hydroxide, magnesium sulfate or a similar magnesium compound, or calcium phosphate, magnesium phosphate or a similar apatite material.
- the nanoparticles can be configured of activated metal, such as vanadium (V), chromium (Cr), manganese (Mn), iron (Fe), cobalt (Co), nickel (Ni), copper (Cu), zinc (Zn) or the like.
- activated metal such as vanadium (V), chromium (Cr), manganese (Mn), iron (Fe), cobalt (Co), nickel (Ni), copper (Cu), zinc (Zn) or the like.
- the nanoparticles have a size for example equal to or smaller than 100 nm, preferably 0.5 nm-10 nm, more preferably 1.0 nm-5 nm.
- the underlying film can have a thickness for example of 2.0 nm-100 nm.
- a gas of a source material for forming a carbon nanotube is supplied to a surface of the substrate having the nanoparticles formed thereon, and the substrate is heated in that condition As a result, a carbon nanotube is grown on the surfaces of the nanoparticles disposed on the surface of the substrate.
- the carbon nanotube thus grown is used to form an assembly portion configured of a plurality of carbon nanotubes assembled together, as will be described hereinafter.
- a CNT assembly formation step (S20) is performed.
- a conventionally well known method is used to strand a plurality of carbon nanotubes that are produced in the step (S10) together to form an assembly portion formed of the carbon nanotubes.
- a conventionally well known method can be used to form the assembly portion of the carbon nanotubes
- a required number of nano-size catalysts can be adjacently placed to grow carbon nanotubes (CNTs) to bond a required number of CNTs together, or furthermore, a plurality of CNTs may have their ends chucked and rotated, and thus formed into a stranded wire.
- a Ga catalyst reaction step (S30) is performed.
- the assembly portion formed of the carbon nanotubes in the step (S20) has a surface exposed to liquid gallium (Ga).
- the a portion formed of the carbon nanotubes has a surface layer converted by the liquid gallium's catalytic reaction to a graphite layer surrounding the assembly portion.
- carbon wire 1 having assembly portion 3 grounded by graphite layer 4 can be obtained.
- the steps (S10) to (S30) correspond to a method of producing carbon wire 1.
- the liquid gallium has a temperature of 450°C-750°C more preferably 550°C-700°C. This can more efficiently cause the liquid gallium's catalytic reaction forming the graphite layer at an outer circumference of assembly portion 3.
- step (S30) of exposing a surface of the assembly portion to liquid gallium to provide a graphite layer is preferably performed while compressive stress is exerted to assembly portion 3.
- Providing graphite layer 4 while assembly portion 3 experiences compressive stress allows carbon wire 1 to be formed with assembly portion 3 configured of carbon nanotubes 2 in contact with one another over an increased area with increased pressure exerted to that area. This further ensures that carbon wire 1 and wire assembly 5 achieve a reduced electrical resistance value.
- the liquid gallium is compressed to exert compressive stress to assembly portion 3, More specifically, an ambient gas that contacts the liquid gallium may be regulated in pressure to compress the liquid gallium.
- the liquid gallium may be held in a bath held in a holding container (a chamber) and an ambient gas (that contacts the liquid gallium) in that chamber may be regulated in pressure.
- the liquid gallium thus compressed can facilitate exerting compressive stress to assembly portion 3.
- the ambient gas regulated in pressure can facilitate regulating a value in pressure applied to the liquid gallium.
- the ambient gas can for example be argon gas, nitrogen gas or an inert gas less reactable with carbon nanotube and liquid gallium.
- the ambient gas's pressure can be set for example at gallium (Ga) vapor pressure to 10 Mpa, more preferably 1 ⁇ 10 -5 torr to 1 Mpa.
- an adhering-Ga removal step (S40) is performed. More specifically, after the graphite layer is provided, i.e., after the step (S30) is performed, carbon wire 1 has removed the gallium adhering on its surface, i.e., the adhering-Ga removal step (S40) is performed to remove gallium adhering to a surface of carbon wire 1 (i.e., a surface of graphite layer 4) provided.
- the gallium can be removed in any method. For example, a solution (e.g., diluted hydrochloric acid or diluted nitric acid) that can dissolve gallium may be sprayed to carbon wire 1, or a bath of the solution can be used to immerse carbon wire 1 therein.
- the steps (S10) to (S40) are performed a plurality of times or the step (S20) is performed to form a plurality of assembly portions formed of carbon nanotubes and the plurality of sombly portions concurrently and in parallel undergo the step (S30) and the step (S40) to obtain a plurality of carbon wires.
- the step (S10) to (S40) indicating a method of producing a carbon wire are used to perform a process for producing a plurality of carbon wires.
- the processing step (S50) is peformed to strand a plurality of carbon wires 1 that are obtained through the step (S10) to the step (S48) together to form wire assembly 5 (see Fig. 3 ).
- any conventionally well known method can be employed to strand the plurality ofcarbon wires 1 together.
- a required number of nano-size catalyst can be adjacently placed to grow CNTs to bond a required number of CNTs together, or furthermore, a plurality of CNTs may have their ends chucked and rotated, and thus formed into a stranded wire Wire assembly 5 formed of carbon wires 1, as shown in Fig. 3 , and low in resistance, can thus be obtained.
- the method of producing carbon wire 1 or wire assembly 5, as described above, allows a portion of a carbon nanotube(s) of assembly portion 3 that is exposed at a surface to be exposed to liquid gallium to obtain graphite layer 4 through the liquid gallium's catalysis (see fig. 1 and Fig. 2 ), as has been described in the step (S30).
- the former allows a process to be performed at a temperature lower than the latter to provide graphite layer 4 to provide the present carbon wire.
- Fig 5 is a. flowchart for illustrating another method of producing a wire assembly according to the preset invention.
- Fig. 6 is a schematic diagram for illustrating a coating step shown in Fig. 5 .
- Fig. 7 is a schematic diagram for illustrating a Ga catalyst ration step shown in Fig. 5 .
- the present invention provides the wire assembly produced in the other method, as will be described hereinafter.
- the Fig. 5 wire assembly production method includes steps basically similar to those of the Fig. 4 wire assembly production method, except that the former has the Ga catalyst reaction step (S30) preceded by the step of providing an amorphous carbon layer as a surface layer of an assembly portion, i.e., a coating step (S60).
- the step (S10) and the step (S20) are initially performed, as done in the Fig. 4 wire assembly production method, and thereafter, as shown in Fig. 6 , on a surface of assembly portion 3 obtained, an amorphous carbon layer 11, which is to serve as graphite layer 4(see Fig. 7 ), is provided.
- Amorphous carbon layer 11 can be provided in any conventional well known method. For example, phenanthrene (C 14 H 10 ), pyrene, methane acetylene or the like may be thermally decomposed to provide amorphous carbon layer 11, or an electron beam or an ion beam may be used to decompose a hydrocarbon based gas. As a result, the Fig. 6 structure is obtained.
- the Ga catalyst reaction step (S30) is performed, This step (S30) can be performed in a method basically similar to the step (S30) performed in the Fig 4 production method. It should be noted, however, that in the Fig. 5 step (S30), amorphous carbon layer 11 has a surface layer converted to graphite layer 4 through the liquid gallium's catalytic reaction. As a result, carbon wire 1 having a structure shown in Fig. 7 can be obtained.
- the Fig. 5 production method can thus provide graphite layer 4 from amorphous carbon layer 11 while maintaining a structure of carbon nanotubes 2 in assembly portion 3. The method thus allows an increased degree of freedom in designing carbon wire 1 in configuration.
- the step (S40) and the step (S50) can be performed to obtain a wire assembly similar in structure to the Fig. 3 wire assembly 5.
- the Fig 5 production method produces a wire assembly configured of carbon wire 1 having amorphous carbon layer 11 posed between carbon nanotube 2 configuring assembly portion 3 and graphite layer 4, as can be seen in Fig. 7 .
- Fig. 8 schematically shows a process for producing electrically conductive film, an electrically conductive substrate, and a transparent, electrically conductive sheet according to the present invention.
- a substrate 17 is exposed to a slurry having carbon nanotubes (hereinafter referred to as CNT(s)) 2 dispersed therein to form a carbon nanotube network (hereinafter referred to as a CNT network) formed of a plurality of CNTs.
- the carbon nanotube network has a surface exposed to Ga vapor to allow the CNT network to have its constituent CNTs linked together by graphite film to obtain electrically conductive film 18 and an electrically Conductive substrate ( Fig. 8 (b) ).
- a resin sheet is brought into contact, at a surface thereof having thermosestting resin or ultraviolet (UV) curable resin thereon, with the surface of electrically conductive film 18 that has the CNT network formed thereon, and the resin sheet is then thermally set or UV-cured to transfer the CNT network to the resin sheet to obtain the present transparent, electrically conductive sheet ( Fig. 8 (c) ).
- Carbon nanotube 2 which is a tube having a lattice structure or carbocyclic six-membered rings, may be a tube structured of a single sheet, i.e., a single-walled carbon nanotube (hereinafter also referred to as "SWNT"), or may be a. tube structured of multiple layers of tubes having the lattice structure of carbocyclic six-membered rings, i.e., a multiwalled-carbon nanotube (hereinafter also referred to as "MWNT").
- SWNT single-walled carbon nanotube
- MWNT multiwalled-carbon nanotube
- an SWNT is more flexible.
- An MWNT is less flexible than the SWNT, and MWNTs having more multiple layers have a tendency to be more rigid. It is desirable that an SWNT of an MWNT be used depending on the purpose, as occasion demands, with their properties considered.
- the carbon nanotube is applicable is not limited to any particular value. In general, however, a carbon nanotube in a range of 10 nm to 1000 ⁇ m, preferably 100 nm to 100 ⁇ m, is used. The carbon nanotube is not limited in diameter (or thickness) to any particular value. In general, however, a carbon nanotube in a range of 1 nm to 50 nm is used, and for an application requiring more transparency, a carbon nanotube in a range of 3 mn to 10 nm is preferably used.
- a slurry having the CNTs dispersed therein is prepared as follows CNTs prepared in an are process are introduced in acetone and bundled CNTs are ultrasonically debundled and dispersed uniformly in the acetone Subsequently, before time elapses, the slurry is sprayed to substrate 17 and dried to form a CNT network on the substrate.
- the acetone may be replaced with alkyl benzene sulfonate or a similar surfactant, a sulfosuccinate diester or a similar solvent having a structure of a hydrophobic moiety-a hydrophilic moiety-a hydrophobic moiety to be used to similarly disperse CNTs therein.
- a dispersant or the like will enter between those portions of CNTs at which the CNTs contact one another. Accordingly, preferably, after the slurry is dried on the substrate, water or acetone is used to wash away the dispersant or other matters adhering to the substrate
- a carbon nanotube network is formed of a plurality of CNTs randomly intertwined with one another on substrate 17 and thus formed in a network.
- a conventional CNT network is large in electrical resistance, as it has its CNTs electrically connected only by the physical contact made at those portions of the CNTs at which the CNTs contact one another.
- the present invention allows a CNT network to be processed with Ga vapor to provide CNTs with a graphite film on their surfaces to link the CNTs together. This can reduce the CNT network's electrical resistance and thus provide electrically conductive film having a low resistance value.
- CNTs may be brought into contact with a substrate to form a CNT network in any method. They may be applied in any of generally used methods. Applicable methods include spin-coating, dip-coating, curtain-coating, roll-coating, applying with a brush, spray-coating and the like, for example. In particular, spin-coating is preferable, as it can easily provide a CNT network in a homogeneous thin film.
- Substrate 17 may be any substrate that is normally used for production of electrically conductive film.
- a substrate formed of glass, mica, quartz or a similar transparent material allows an electrically conductive substrate as a whole to have significantly increased transparency.
- carbon vapor deposition, meta vapor deposition or the like to provide a surface of a substrate with electrical conductance
- employing a carbon nanotube network to provide a surface of substrate 17 with electrical conductance can eliminate the necessity of completely covering the surface with carbon nanotube
- the network has gaps, and thus allows an electrically conductive substrate to have significantly high optical transmittance for a predetermined surface conductivity.
- Electrically conductive film 18 produced according to the method of the present invention is electrically conductive film having a carbon nanotube network formed of a plurality of carbon nanotubes linked together by graphite film.
- the electrically conductive film has the CNTs electrically connected via the graphite film, and thus has a low resistance value characteristically.
- the electrically conductive substrate produced according to the method of the present invention is an electrically conductive substrate formed of substrate 17 and electrically conductive film 18 provided on substrate 17 and having a carbon nanotube network formed of a plurality of carbon nanotubes linked together by graphite film.
- the electrically conductive substrate has CNTs thereon electrically connected via the graphite film, and thus has a low resistance value characteristically.
- Resin sheet 4 may be of any highly transparent resin that is normally used as a substrate.
- polymeric (PET) film having epoxy resin or similar thermosetting resin, or acrylic syrup or similar UV curable resin or similar curable resin applied thereon is used, as it allows the CNT network formed on the electrically conductive film to be transferred efficiently.
- the method of producing electrically conductive film, an electrically conductive substrate and a transparent, electrically conductive sheet in accordance with the present invention will more specifically be described hereinafter for the step of providing graphite film on a CNT network.
- Fig. 9 is a schematic cross section of one example of a graphite film production apparatus used in the present invention.
- the present invention employs a graphite film production apparatus configured of a quartz reaction tube 6 and an alumina container 20 provided in quartz reaction tube 6 and having liquid Ga 9 introduced therein.
- Substrate 17 with a plurality of carbon nanotubes 2 formed thereon in a CNT network is to be processed, placed in a vicinity of alumina container 20.
- a heater 7 is provided for the reaction tube to regulase the internal temperature of quartz reaction tube 6.
- Substrate 17 may be a conventionally well known substrate that is normally used for production of electrically conductive film. However, a substrate formed of glass, mica, quartz or a similar transparent material allows an electrically conductive film as a whole to have significantly increased transparency.
- the CNT network formed of a plurality carbon nanotubes 2 may be formed in any convention well known method.
- the methos includes spin-coating, dip-coating, curtain-coating, roll-coating, applying with a brush, spray-coating and the like, for example.
- spin-coating is preferable, as it can easily provide a CNT network in a homogeneous thin film. Subsequently, preferably, this substrate is washed to prevent the CNT network from having a dispersant or similar impurity remaining therein.
- a roller or the like is preferably used to firmly compress the CNT network from above.
- amorphous carbon film is provided on the CNT network to ensure that graphite film is provided.
- the amorphous carbon film may be provided in any conventional well known method. For example, phenanthrene (C 14 H 10 ). pyrene, methane acetylene or the like may be thermally decomposed to provide the amorphous carbon film, or an electron beam or an ion beam may be used to decompose a hydrocarbon based gas.
- the amorphous carbon film preferably has a thickness equal to or smaller than 10 nm, as such film can enhance transparency.
- a substrate to be processed is secured in quartz reaction tube 6 horizontally, and a turbo pump is used to vacuum the background to 10 -6 Torr or lower.
- Heater 7 heats the reaction tube to evaporate liquid Ga 9 in quartz reaction tube 6 and beats Ga vapor 5 to 600°C or higher to bring the vapor into contact with a surface of the CNT network formed of a plurality of carbon nanotubes 2, More preferably, Ga vapor 5 is heated to 800°C or higher to enhance the catalysis of Ga vapor 5.
- the above heat treatment is conducted for 10 minutes to 1 hour, and subsequently the reaction tube is slowly cooled to again attain room temperature.
- the heat treatment in Ga vapor 5 provides graphite film on a surface of the CNT network formed of carbon nanotubes 2.
- electrically conductive film having a carbon nanotube network formed of a plurality of carbon nanotubes linked together by graphite film is provided, and an electrically conductive substrate is thus obtained.
- the electrically inductive film produced in the aforementioned process is used to produce a transparent, electrically conductive sheet in a method, as will be described hereinafter.
- a sheet of resin is brought into contact with that surface of the aforementioned electrically conductive substrate which has the CNT network formed thereon to transfer the CNT network to the sheet of resin.
- thermosetting resin or UV curable resin is applied to that surface of the sheet of resin which is bought into contact with the CNT network.
- the sheet of resin is set/cured to secure the CNT network to the sheet of resin to produce a transparent, electrically conductive sheet.
- Fig. 10 is a schematic cross section of one example of a graphite film production apparatus used in the present invention.
- the present invention employs a graphite film production apparatus configured of quartz reaction tube 6 and alumina container 20 provided in quartz reaction tube 6 and having liquid Ga 1 introduced therein.
- Substrate 17 with amorphous carbon film 21 provided thereon is to be processed, placed in a vicinity of alumina container 20.
- heater 7 is provided for the reaction tube to regulate the internal temperature of quartz reaction tube 6.
- Substrate 17 may be a conventionally well known substrate that is used as a substrate for production of electrically conductive film.
- a substrate for production of electrically conductive film Preferably, an SiC, Ni, Fe, Mo, Pt or similar, monocrystalline substrate is used, as monocrystalline graphite film can be obtained.
- Amorphous carbon film 21 may be provided in any conventional well known method.
- phenanthrene (C 14 H 10 ), pyrene, methane acetylene or the like may be thermally decompose to provide amorphous carbon film 2, or an electron beam or an ion beam may be used to decompose a hydrocarbon based gas.
- Amorphous carbon film 21 preferably has a thickness set to match that of graphene film or graphite film targeted.
- a substrate to be processed is secured in quartz reaction tube 6 horizontally, and a turbo pump is used to vacuum the background to 10 -6 Torr or lower.
- Heater 7 heats the reaction tube to evaporate liquid Ga 9 in quartz reaction tube 6 and heats Ga vapor 5 to 600°C or higher to bring the vapor into contact with a surface of amorphous carbon film 21.
- the above heat treatment is conducted for 10 minutes to 1 hour, and subsequently the reaction tube is slowly cooled to again attain room temperature.
- the beat treatment in Ga vapor 5 provides graphite film on a surface of amorphous carbon film 21.
- Fig. 11 is a schematic cross section of one example of a graphite film production apparatus used in the present invention when Ga vapor has unifom vapor pressure at a surface of a carbon source.
- a second embodiment employs a graphite film production apparatus having quartz reaction tube 6 and a subordinate Ga reaction chamber 22 provided in quartz reaction tube 6 and accommodating alumina container 20 having liquid Ga 9 introduced therein, and substrate 17 having amorphous carbon film 21 thereon, i.e., a substrate to be processed.
- Subordinate Ga reaction chamber 22 has a wall having a differential evacuation in the form of a small gap.
- the first embodiment shows a graphite film production apparatus having quartz reaction tube 6 internally filled with Ga vapor 5 generated from liquid Ga 9.
- quartz reaction tube 6 internally filled with Ga vapor 5 generated from liquid Ga 9.
- portions of quartz reaction tube 6 that are remoter from heater 7 are lower in temperature, and some of them have room temperature.
- Ga vapor 5 varies in temperature at different locations and thus does not have uniform vapor pressure.
- quartz reaction tube 6 that has subordinate Ga reaction chamber 22 therein allows Ga vapor 5 to be held in subordinate Ga reaction chamber 22 and thus have a fixed vapor pressure. Furthermore, subordinate Ga reaction chamber 22 that accommodates therein alumina container 20 having liquid Ga 9 introduced therein, and substrate 17 having amorphous carbon film 21 thereon, or a substrate to be processed, and that is vacuumed through a small gap serving as a differential evacuation port, can internally have a Ga vapor pressure of a possible maximal value and also provide a uniform Ga vapor pressure in a vicinity of the substrate to be processed.
- the aforementioned production method can provide graphite film having a surface without inconsistency in color or roughness and thus having a significantly smooth mirror surface.
- a substrate to be processed is secured in quartz reaction tube 6 horizontally, and a turbo pump is used to vacuum the background to 10 -6 Torr or lower.
- Heater 7 heats the reaction tube to evaporate liquid Ga 9 in quartz reaction tube 6 and heats Ga vapor 5 to 600°C or higher to bring the vapor into contact with a surface of amorphous carbon film 21. More preferably, Ga vapor 5 is heated to 800°C or higher to enhance the catalysis of Ga vapor .5.
- the heat treatment in Ga vapor 5 provides graphite film on a surface of amorphous carbon film 21.
- Fig. 12 is a schematic cross section of one example of a graphite film production apparatus employed in the present invention with Ga vapor plasmatized.
- a third embodiment employs a graphite film production apparatus having quartz reaction tube 6 accommodating alumina container 20 having liquid Ga 9 introduced therein, and a plasma producing electrode 10, with a heater 12 provided at the alumina container for Ga.
- Substrate 17 with amorphous carbon film 21 thereon, or a substrate to be processed, is positioned in a vicinity of alumina container 20 between paired plasma producing electrodes 10 and exposed to a Ga plasma 23.
- heater 7 is provided for the reaction tube to regulate the internal temperature of quartz reaction tube 6.
- Ga vapor to obtain graphite film is an effective technique to obtain a single or multiple layers of large-area graphite film and is a practical technique directed to electronics device applications.
- a process using Ga vapor must be performed a plurality of times to repeat a reaction until electrically conductive film as predetermined is obtained.
- Ga vapor can be plasmatized and thus provided with energy to serve as a catalyst to graphitize amorphous carbon.
- the former can provide graphite film larger in thickness.
- using Ga plasma allows graphitization to be observed on a substrate having as low a temperature as approximately 400°C, and can thus induce graphitization at a lower temperature
- graphite film must be provided directly on a silicon device, and accordingly, it is essential to perform the process at low temperature.
- plasmatizing Ga vapor to allow graphite film to be provided in a process performed at low temperature is significantly effective for integration with the silicon device process.
- a substrate to be processed is secured in quartz reaction tube 6 horizontally, and a turbo pump is used to vacuum the background to 10 -6 Torr or lower.
- Heater 12 for Ga is operated to facilitate evaporating liquid Ga 9, while plasma producing electrodes 10 are used to plasmatize Ga vapor present at a location sandwiched between the electrodes, and heater 7 for the reaction tube is also used to heat the substrate exposed to Ga plasma 11 to 400°C or higher and Ga plasma 23 is brought into contact with a surface of amorphous carbon film 21.
- the substrate to be processed in contact with Ga plasma 23 has a temperature more preferably of 800°C or higher.
- the heat treatment in Ga plasma 23 converts amorphous carbon film 21 at least partially or entirely to graphite film.
- Fig. 13 is a schematic cross section of one example of a graphite film production apparatus employed in the present invention with a carbon source of a hydrocarbon gas.
- a fourth embodiment employs a graphite film production apparatus having quartz reaction tube 6 connected to a Ga vapor supply unit 15 and a hydrocarbon gas supply unit 13.
- Ga vapor supply unit 15 receives liquid Ga 9, which is heated by a heater for Ga and thus evaporated to supply Ga vapor 5 to the interior of quartz reaction tube 6.
- Hydrocarbon gas supply unit 13 receives hydxocarbon material serving as carbon material, such as camphor, phenanthrene, pyrene or the like, to supply a carbon source as hydrocarbon gas to the interior of quartz reaction tube 6.
- Quartz reaction tube 6 accommodates substrate 17 therein as a substrate to be processed
- Quartz reaction tube 6 receives the hydrocarbon gas, which reacts with Ga vapor in a vicinity of substrate 17, therewhile the gas is decomposed and thus rapidly forms graphite film on substrate 17.
- the Ga can disadvantageously be introduced into the film.
- the substrate has a temperature of 600°C or higher, the Ga is hardly introduced into the film.
- the substrate has a low temperature of 600°C or lower, and the Ga is accordingly introduced into the graphite film, annealing at approximately 500°C for a long period of time allows Ga to be separated and thus removed from the film.
- a substrate to be processed is secured in quartz reaction tube 6 horizontally, and a turbo pump is used to vacuum the background to 10 -6 Torr or lower.
- Heater 12 for Ga is operated to evaporate liquid Ga 9 to supply Ga vapor to the interior of quartz reaction tube 6. while a valve 16 located between hydrocarbon gas supply unit 13 and quartz reaction tube 6 is opened to supply hydrocarbon gas.
- Heater 7 for the reaction tube is operated to heat quartz reaction tube 6 to heat Ga vapor 5 therein to 400°C or higher and bring Ga vapor 5 into contact with a surface of substrate 3.
- Ga vapor 5 has a temperature more preferably of 800°C or higher.
- the heat treatment in Ga vapor 5 provides graphite film on substrate 17.
- An arc process is employed to produce unpurified single-walled carbon nanotubes (CNTs), which are used to form an assembly portion provided as a 0.3 mm-diameter wire formed of stranded CNT filaments.
- the wire formed of stranded CNT filaments has a length of 10 mm.
- the wire formed of stranded CNT filaments is immersed for one hour in liquid gallium (Ga) heated to 600°C. In doing so, an ambient gas of Ar is used, set at a pressure of 1 ⁇ 10 -5 Torr.
- the wire formed of stranded CNT filaments is drawn out of the liquid Ga and has Ga that adheres to its surface removed therefrom with diluted hydrochloric acid.
- the wire formed of stranded CNT filaments is thus provided with a graphite layer on a surface thereof, i.e., a carbon wire is obtained.
- the graphite layer has a thickness of approximately 5 ⁇ m.
- the carbon wire having the graphite layer is subjected to measurment of electrical resistance by a 4-terminal method.
- the carbon wire having the graphite layer has a value in electrical resistance decreased to approximately 1 / 5 of that of a sample of a comparative example 1 described later.
- An are process is employed to produce unpurified single-walled carbon nanotubes (CNTs), which are used to form an assembly portion provided as a 5 ⁇ m-diameter wire formed of stranded CNT filaments.
- the wire formed of stranded CNT filaments has a length of 10 mm.
- phenanthrene (C 14 H 10 ) is thermally decomposed to provide an amorphous carbon layer on a surface of the wire formed of stranded CNT filaments.
- the wire formed of stranded CNT filaments is immersed for one hour in liquid gallium (Ga) heated to 600°C.
- Ga liquid gallium
- an ambient gas of Ar is used, set at a pressure of 2 atmospheres.
- the wire formed of stranded CNT filaments is drawn out of the liquid Ga and has Ga that adheres to its surface removed therefrom with diluted hydrochloric acid.
- the wire formed of stranded CNT filaments is thus provided with a graphite layer on a surface thereof, i.e., a carbon wire is obtained.
- the graphite layer has a thickness of approximately 1 ⁇ m.
- the carbon wire having the graphite layer is subjected to measurement of electrical resistance by a 4-terminal method.
- the carbon wire having the graphite layer has a value in electrical resistance decreased to approximately 1 20 of that of the comparative example for example 1 of the present invention.
- the carbon wire is considered to have an interior having a plurality of carbon nanotubes substantially integrated together.
- CNTs carbon nanotubes
- phenanthrene (C 14 H 10 ) is thermally decomposed to provide an amorphous carbon layer on a surface of the wire formed of bonded CNT filaments.
- the wire formed of bonded CNT filaments is immersed for one hour in liquid gallium (Ga) heated to 500°C.
- an ambient gas of argon (Ar) is used, set at a pressure of 10 atmospheres is order to allow the wire to have its internal carbon nanotubes brought into close contact with one another.
- the wire formed of bonded CNT filaments is drawn out of the liquid Ga and has Ga that adheres to its surface removed therefrom with diluted hydrochloric acid.
- the wire formed of bonded CNT filaments is thus provided with a graphite layer on a surface thereof, i.e., a carbon wire is obtained.
- the graphite layer has a thickness of approximately 0.2 ⁇ m. Furthermore, it has been found that the graphite layer is formed in successive rings wrapping the internal CNTs and has thus become carbon nanotube (CNT).
- the carbon wire having the graphite layer is subjected to measurement of electrical resistance by a 4-terminal method.
- the carbon wire having the graphite layer has a value in electrical resistance smaller than the comparative example by one digit. This is probably because the carbon wire has an interior having carbon nanotubes in close contact with one another and thus integrated together.
- Catalytic CVD is employed to prepare a 30 nm-diameter, 500 ⁇ m long multiwalled carbon nanotube (CNT), and such CNTs are overlapped by 200 ⁇ m to form an assembly portion implemented as a wire formed of bonded CNT filaments.
- the wire formed of bonded CNT filaments has a length of 10 mm and a diamer of 0.6 ⁇ m
- the wire formed of bonded CNT filaments is immersed for one hour in liquid gallium (Ga) heated to 550°C. More specifically, the liquid gallium and the wire formed of bonded CNT filaments are enclosed in a capsule of stainless steel. The capsule is surrounded by an ambient gas of argon (Ar). The ambient gas is compressed to exert pressure to the liquid gallium and the wire of bonded CNT filaments together with the capsule. The pressure is set at 100 atmospheres to allow the wire of bonded CNT filaments to have its internal carbon nanotubes brought into close contact with one another.
- Ar argon
- the wire formed of bonded CNT filaments is drawn out of the liquid Ga and has Ga that adheres to its surface removed therefrom with diluted hydrochloric acid.
- the wire formed of bonded CNT filaments is thus provided with a graphite layer on a surface thereof, i.e., a carbon wire is obtained.
- the graphite layer has a thickness of approximately 80 nm. Furthermore, it has been found that the graphite layer is formed in successive rings wrapping the internal CNTs and has thus become carbon nanobube (CNT).
- Such carbon wires each having the graphite layer are bundled and stranded together to provide a stranded wire to produce a 0.5 ⁇ m-diameter stranded wire, Then, as has been done in an above-described step, the stranded wire is immersed in liquid Ga to bond together a plurality of carbon wires configuring the stranded wire (i.e., a graphite layer is formed on a surface of a bundle of a plurality of carbon wires to surround the bundle).
- the carbon wire having the graphite layer is subjected to measurement of electrical resistance by a 4-terminal method.
- the carbon wire having the graphite layer has a value in electrical resistance smaller than the comparative example by two digits or larger. This is probably because the carbon wire has an interior having carbon nanotubes in close contact with one another and thus integrated together.
- An arc process is employed to produce unpurified, single-walled carbon nanotubes (CNTs) which are in turn used to form an assembly portion implemented as a 0.3 mm-diameter wire formed of stranded CNT filaments.
- the wire formed of stranded CNT filaments has a length of 10 mm.
- the wire formed of stranded CNT filaments is subjected to measurement of electrical resistance by a 4-terminal method.
- the comparative example's wire formed of stranded CNT filaments has a value in electrical resistance of 7.8 ⁇ 10 -3 ⁇ •cm. This value is larger than that of copper by three digits or larger
- An arc process is employed to produce unpurified, single-walled carbon nanotubes (CNTs) which are in turn used to form an assembly portion implemented as a 0.3 mm-diameter wire formed of stranded CNT filaments.
- the wire formed of stranded CNT filaments has a length of 10 mm.
- the wire formed of stranded CNT filaments is immersed for one hour in liquid gallium (Ga) heated to 800°C. In doing so, an ambient gas of Ar is used, set at a pressure of 1 ⁇ 10 -5 Torr.
- the wire of stranded CNT filaments immersed in the liquid Ga has been decomposed in the liquid Ga and thus disappeared. Accordingly, it is preferable that the wire formed of stranded CNT filaments be immersed in liquid gallium heated to a temperature lower than 800°C, more preferably 750°C or lower.
- a ceramic substrate is prepared and thereon a slurry having CNTs dispersed therein is sprayed and then dried to form a CNT network on the substrate.
- an amorphous carbon film of approximately 5 nm on average is provided on the CNT network by laser abrasion.
- the Fig. 9 graphite film production apparatus is employed to produce graphite film.
- Quartz reaction tube 6 accommodates an approximately 1 cm-diameter alumina container having liquid Ga 9 introduced therein, and in a vicinity thereof, substrate 17 bearing a plurality of carbon nanotubes 2 forming a CNT network is placed as a substrate to be processed.
- a substrate to be processed is secured in quartz reaction tube 6 horizontally, and a turbo pump is used to vacuum the background to 10 -6 Torr or lower.
- Heater 7 for the reaction tube is operated to beat Ga vapor 5 to 650°C to perform a process for one hour and subsequently the reaction tube is slowly cooled again to room temperature.
- comparative examples 3 and 4 are sample substrates which do not undergo the process with Ga vapor.
- the beat treatment with Ga vapor provides graphite film on a surface of the CNT networks
- the treatment's temperature and the processed substrate's sheet resistance value are as shown in table 1. Note that the sheet resistance value is measured in a 4-terminal method.
- thermosetting resin on a surface that is brought into contact with the CNT network is deposited from above, and then thermally set to transfer and secure the CNT network to the thermosetting resin to obtain a transparent, electrically conductive sheet, which has a sheet resistanee value as shown in table 1.
- a glass substrate is prepared and thereon a slurry having CNTs dispersed therein is sprayed and then dried to form a CNT network on the substrate.
- the substrate is washed with water and acetone to prevent a dispersant or a similar impurity from remaining on the CNT network.
- an organic gas phenanthrene (C 14 H 10 )
- phenanthrene C 14 H 10
- the Fig. 9 graphite film production apparatus is employed to produce graphite film.
- Quartz reaction tube 6 accommodates an approximately 1 cm-diameter alumina container having liquid Ga 9 introduced therein, and in a vicinity thereof, substrate 17 bearing a plurality of carbon nanotubes 2 forming a CNT network is placed as a substrate to be processed.
- a substrate to be processed is secured in quartz reaction tube 6 horizontally, and a turbo pump is used to vacuum the background to 10 -6 Torr or lower.
- Heater 7 for the reaction tube is operated to heat Ga vapor 5 to 750°C to perform a process for 10 minutes and subsequently the reaction tube is slowly cooled again to room temperature.
- comparative examples 5 and 6 are sample substrates which do not undergo the process with Ga vapor.
- the heat treatment with Ga vapor provides graphite film on a surface of the CNT network.
- the treatment's temperature and the processed substrate's sheet resistance value are as shown in table 2. Note that the sheet resistance value is measured in a 4-terminal method.
- a resin sheet having thermosetting resin on a surface that is brought into contact with the CNT network is deposited from above, and then thermally set to transfer and secure the CNT network to the thermosetting resin to obtain a transparent, electrically conductive sheet, which has a sheet resistance value as shown in table 2.
- Table 2 Examples Comparative Examples 7 8 5 6 Amorphous carbon film + - + - Ga vapor process + + - - Ga process temperature (°C) 750 750 - - Process time 10 min 10 min - - Transparent, electrically conductive sheet's sheet resistance value (k ⁇ /square) 5 10 300 800
- the Fig. 10 graphite film production apparatus is employed to produce graphite film.
- Quartz reaction tube 6 accommodates an approximately 1 cm-diameter alumina container having liquid Ga introduced therein, and in a vicinity thereof, substrate 17 bearing amorphous carbon film 21 is placed as a substrate to be processed.
- the substrate to be processed is a silicon substrate having a surface with an approximately 500 nm thick thermal oxide film thereon and an amorphous carbon film provided at that surface by laser abrasion.
- a substrate to be processed is secured in quartz reaction tube 6 horizontally, and a turbo pump is used to vacuum the background to 10 -6 Torr or lower.
- Heater 7 for the reaction tube is operated to heat Ga vapor 5 to a temperature indicated in table 3 to perform a process for one hour, and the reaction tube is slowly cooled again to room temperature.
- Examples 9-11 provide approximately 3-5 layers of graphite film on a surface of amorphous carbon film through the heat treatment in Ga vapor.
- Each sample substrate has a significantly smooth mirror surface without variation in color, or roughness.
- amorphous carbon deposition and Ga process are repeated until substrate 3 has amorphous carbon film and graphite film thereon together forming a film having a thickness of approximately 50 nm.
- Each resultant sample substrate has a sheet resistance value, as shown in table 3.
- a substrate to be processed which is similar to those of the examples of the present invention is thermally treated in quartz reaction tube 6 at 600°C without liquid Ga 1 introduced therein. In other words, the substrate simply undergoes the heat treatment without subjecting amorphous carbon film to the Ga process. The other steps are performed similarly as done is the above examples of the present invention.
- the resultant sample substrate has a sheet resistance value as shown in table 3. Table 3 Examples Comparative Examples 9 10 11 7 8 Process temperature (°C) 600 700 800 200 600 Sheet resistance value (k ⁇ /square) 100 20 6 ⁇ 1500
- the Fig. 11 graphite film production apparatus is employed to produce graphite film.
- Quartz reaction tube 6 accommodates subordinate Ga reaction chamber 22 accommodating an approximately 1 cm-diameter alumina container having liquid Ga 9 introduced therein, and in a vicinity thereof, substrate 17 bearing amorphous carbon film 21 is placed as a substrate to be processed.
- the substrate to be processed is a silicon substrate having a surface with an approximately 500 nm thick thermal oxide film thereon and an amorphous carbon film provided at that surface by laser abrasion.
- a substrate to be processed is secured in subordinate Ga reaction chamber 22 horizontally, and a turbo pump is used to vacuum the background to 10 -6 Torr or lower.
- Heater 7 for the reaction tube is operated to heat Ga vapor 5 in subordinate Ga reaction chamber 22 to a temperature indicated in table 4 to perform a process for 10 minutes, and the reaction tube is slowly cooled again to room temperature.
- Examples 12-14 provide approximately 3-5 layers of graphite film on a surface of amorphous carbon film through the heat treatment in Ga vapor.
- Each sample substrate has a significantly smooth mirror surface without variation in color, or roughness.
- the aforementioned amorphous carbon deposition and Ga process are repeated until substrate 17 has amorphous carbon film and graphite film thereon together forming a film having a thickness of approximately 100 nm.
- the process's temperature and the resultant sample substrate's sheet resistance value are as shown in table 4.
- a substrate to be processed which is similar to those of the examples of the present invention is thermally treated in quartz reaction tube 6 at 600°C for 10 minutes without liquid Ga 1 introduced therein.
- the substrate simply undergoes the heat treatment without subjecting amorphous carbon film to the Ga process.
- the other steps are performed similarly as done in the above examples of the present invention.
- the resultant sample substrate has a sheet resistance value as shown in table 4.
- the Fig. 12 graphite film production apparatus is employed to produce graphite film.
- Quartz reaction tube 6 accommodates a pair of plasma producing electrodes 10 therein, and in a vicinity thereof, alumina container 20 having a diameter of approximately 1 cm and having liquid Ga 1 introduced therein is placed. At the alumina container, heater 12 is placed for Ga. Substrate 17 bearing amorphous carbon film 21 thereof is placed between plasma producing electrodes 10 as a substrate to be processed.
- the substrate to be processed is a silicon substrate having a surface with an approximately 500 nm thick thermal oxide film thereon and an amorphous carbon film provided at that surface by laser abrasion.
- a substrate to be processed is secured between plasma producing electrodes 10 horizontally, and a turbo pump is used to vacuum the background to 10 -6 Torr or lower.
- Heater 12 for Ga is operated to facilitate evaporating liquid Ga 9, while plasma producing electrodes 10 are used to plasmatize Ga vapor present at a location sandwiched between the electrodes, and heater 7 for the reaction tube is also used to heat the substrate in contact with Ga plasma 23 to a temperature indicated in table 5 and a 10-minute process is also performed, and the reaction tube is slowly cooled again to room temperature.
- Examples 15-17 each provide approximately 3-5 layers of graphite film on a surface of the substrate through the heat treatment in Ga plasma.
- Each sample substrate has a significantly smooth mirror surface without variation in color, or roughness.
- the aforementioned amorphous carbon deposition and Ga process are repeated until substrate 17 has amorphous carbon film and graphite film thereon together forming a film having a thickness of approximately 100 nm.
- the process's temperature and the resultant sample substrate's sheet resistance value are as shown in table 5.
- a substrate to be processed which is similar to those of the examples of the present invention is thermally treated in quartz reaction tubs 6 at 600°C for 10 minutes without liquid Ga 9 introduced therein.
- the substrate simply undergoes the heat treatment without subjecting amorphous carbon film to the Ga process.
- the other steps are performed similarly as done in the above examples of the present invention.
- the resultant sample substrate has a sheet resistance value as shown in table 5.
- the Fig. 13 graphite film production apparatus is employed to produce graphite film.
- Quartz reaction tube 6 is connected to Ga vapor supply unit 15 and hydrocarbon gas supply unit 13.
- Ga vapor supply unit 15 has liquid Ga introduced therein.
- Hydrocarbon gas supply unit 13 has phenanthrene introduced therein as a carbon source material.
- substrate 17 is placed in quartz reaction tube 6.
- a substrate to be processed is secured in quartz reaction tube 6 horizontally, and a turbo pump is used to vacuum the background to 10 -6 Torr or lower.
- Heater 12 for Ga is used to evaporate liquid Ga 9 to supply Ga vapor to the interior of quartz reaction tube 6, while valve 16 located between hydrocarbon gas supply unit 13 having phenanthrene introduced therein and quartz reaction tube 6 is opened to supply hydrocarbon gas.
- Heater 7 for the reaction tube is operated to raise the temperature in quartz reaction tube 6 to that indicated in table 6 and a 30-minute process is performed, and the reaction tube is slowly cooled again to room temperature.
- Examples 18-20 each provide graphite film on a surface of the substrate through the heat treatment in Ga vapor to have a thickness of 200 nm.
- Each sample substrate has a significantly smooth mirror surface without variation in color, or roughness.
- the process's temperature and the resultant sample substrate's sheet resistance value are as shown in table 6.
- a substrate to be processed which is similar to those of the examples of the present invention is thermally treated in quartz reaction tube 6 at 600°C for 30 minutes without liquid Ga 9 introduced therein. In other words, the substrate simply undergoes the heat treatment without subjecting amorphous carbon film to the Ga process. The other steps are performed similarly as done in the above examples of the present invention.
- the resultant sample substrate has a sheet resistance value as shown in table 6. Table 6 Examples Comparative Examples 18 19 20 13 14 Process temperature (°C) 400 600 800 200 600 Sheet resistance value (k ⁇ /square) 160 40 2 ⁇ 1500
- the present invention is advantageously applicable particularly to carbon wires configured of a plurality of short carbon nanotubes combined together, and wire assemblies employing such carbon wires.
- the present invention allows mass production of a significantly thin stack of graphite layers or a monolayer of graphite film in large areas.
- the monolayer of graphite film having a large area can be used to allow application to an LSI or similar, large scale graphene integrated circuit.
- increasing thickness allows a transparent, electrically conductive sheet having a large area to be formed, and it is expected to be applied to a large size liquid crystal display.
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Description
- The present invention relates generally to carbon wires, wire assemblies and methods of producing the same, and particularly to carbon wires, wire assemblies and methods of producing the same, that employ a plurality of carbon filaments.
- The present invention also relates to electrically conductive film, electrically conductive substrates, and transparent, electrically conductive sheet including graphite film, that are obtained by exposing a carbon nanotube network to Ga vapor, and methods of producing the same.
- The present invention also relates to methods of obtaining graphite film by exposing a carbon source to Ga vapor.
- As one example of a carbon filament, a carbon nanotube (CNT) has excellent properties and is accordingly expected to be employed in a variety of industrial applications. For example, a CNT provides substantially as low an electrical resistance value as copper and is thus considered to be used as a material for wire. Furthermore, such CNT is produced in a variety of methods, as proposed for example in Japanese Patent Laying-Open No.
2007-112662 - Japanese Patent Laying-Open No.
2007-112662 - When a carbon atom is chemically bonded by an sp2 hybridized orbital, it forms a lattice-structured film having two dimensionally spread carbocyclic six-membered rings packed in a plane. This carbon atom's two dimensional planar structure is referred to as graphene. As a special example, graphene in a tubular closed structure is a carbon nanotube, and graphene layers stacked in a direction of a normal thereto are graphite.
- A carbon nanotube is a tabular material having a diameter equal to or smaller than 1 µm, and ideally, a film in a lattice structure of carbocyclic six-membered rings has planes parallel to a tube's axis to form the tube, and a multiple of such tubes may be provided. The carbon nanotube is theoretically expected to exhibit a metallic property or a semiconducting property depending on how the lattice structured films have carbocyclic six-membered rings linked and the tube's thickness, and it is thus expected as a future high-porformance material.
- For example, Japanese Patent Laying-Open No.
2007-63051 2002-255528 2003-238126 2000-86219 - Graphite has a variety of electrical properties, as observed on graphite film, such as a bandgap, a fractional quantum Hall effect and the like varying with in what size it is cut out, and is thus gaining a large attention in recent years not only for physical phenomena but also in terms of application to devices in the future.
- K. S, Novoselov et. al., Science 306 (2004) pp. 666-669. (Non Patent Document 1). K. S. Novoselov et. al., Proc. Natl. Acad. Sci. U.S.A, 102 (2005) pp. 10451-10453. (Non Patent Document 2), C. Berger et. al., J. Phys. Chem. B108 (2004) pp. 19912-19916. (Non Patent Document 3), and Yuanbo Zhang et. al., Nature 438, pp. 201-204 (10 November, 2005) (Non Patent Document 4) disclose techniques used to produce a monolayer of graphite film, i.e., graphene.
- Typical conventional techniques are provided by K.S. Novoselov et. al., Science 306 (2004) pp. 666-669 (Non Patent Document 1), and K.S. Novoselov et. al., Proc. Natl. Acad. Sci. U.S.A 102 (2005) pp. 10451-10453. (Non Patent Document 2). More specifically, Scotch tape is stuck on graphite crystal to peel off graphite to leave a single sheet of graphene on a silicon substrate having a surface oxidized and a monolayer of graphene is found and utilized. This technique is a rather primitive technique.
- C. Berger et. al., J. Phys. Chem. B108 (2004) pp. 19912-19916. (Non Patent Document 3) discloses that a high temperature process at 1400-1600°C is performed in an environment of ultrahigh vacuum to decompose a SiC monocrystalline surface and after Si is selectively sublimated a monolayer of graphene is synthesized. Furthermore, it is also disclosed that a diamond microcrystal is first formed and then processed at 1600°C to obtain graphene from diamond.
- Yuanbo Zhang et. al., Nature 438, pp. 201-204 (10 November, 2005) (Non Patent Document 4) discloses a method employing chemical vapor deposition to produce graphene. More specifically, camphor vapor is thermally decomposed at 700-850°C at an Ni crystal face to obtain graphene.
- It is difficult, however, to use these methods to handle general, industrial production, and furthermore, the methods cannot provide a large area of graphite film essential to device application.
US2007/284557 A1 relates to a graphene film as a transparent and electrically conducting material.WO 2008/051302 A1 relates to end-to-end joining of nanotubes.JP 2007115903 A -
- Patent Document 1: Japanese Patent Laying-Open No.
2007-112662 - Patent Document 2: Japanese Patent Laying-Open No.
2007-63051 - Patent Document 3: Japanese Patent Laying-Open No.
2002-255528 - Patent Document 4: Japanese Patent Laying-Open No.
2003-238126 - Patent Document 5: Japanese Patent Laying-Open No.
2000-86219 -
- Non Patent Document 1: K. S. Novoselov et. al., Science 306 (2004) pp. 666-669.
- Non Patent Document 2: K. S. Novoselov et. al., Proc. Natl. Acad. Sci U.S.A. 102 (2005) pp. 10451-10453.
- Non Patent Document 3: C. Berger et. al., J. Phys. Chem. B108 (2004) pp. 19912-19916.
- Non Patent Document 4: Yuanbo Zhang et. al., Nature 438, pp. 201-204 (10 November, 2005)
- The above described conventional CNT production methods focus on controlling CNT as a single CNT in size or the like. When CNT's industrial application is considered, however, it would be necessary to assemble a plurality of such CNTs to produce elongate wire (or carbon wire). As the present inventors have studied, while a single CNT is of significantly low resistance, such a plurality of CNTs (each having a length for example of several tens to several hundreds µm) collected (e.g., stranded) together to provide wire (or carbon wire) exhibit as carbon wire an electrical resistance value higher by approximately 3 digits than copper wire.
- The present invention has been made to overcome such disadvantage as described above, and it contemplates a carbon wire employing CNT or a similar carbon filament having a sufficiently low electrical resistance value, and a wire assembly employing the carbon wire.
- Furthermore, the present invention also contemplates electrically conductive film having a carbon nanotube network formed of a plurality of low resistance carbon nanotubes linked together by graphite film, an electrically conductive substrate and a transparent, electrically conductive sheet employing the same, and a method for reproducibly producing the same.
- Furthermore, the present invention also contemplates a method of producing graphite film that can facilitate synthesizing a large area of graphite film significantly reproducibly.
- The present invention provides a method of producing carbon wire according to claim 1, a method of producing electrically conductive film according to claim 9, a method of forming an electrically conductive substrate according to
claim 12, and a method of producing a transparent, electrically conductive sheet according to claim 15. According to a reference example, a carbon wire includes an assembly portion and a graphite layer. The assembly portion is formed of a plurality of carbon filaments in contact with one another. The graphite layer is provided at an outer circumference of the assembly portion. - Thus the carbon wire can have an outer circumferential graphite layer holding an assembly portion to ensure that the assembly portion has its carbon filaments in contact with one another. This allows the assembly portion to have the carbon filaments in contact with one another over an increased area with increased pressure exerted to that area. This can prevent the assembly portion from having the carbon filaments in contact with one another insufficiently and the carbon wire from accordingly having an increased electrical resistance value. Furthermore, the graphite layer can also act as an electrically conductive layer to allow the carbon wire to have a further reduced electrical resistance value.
- In the above carbon wire, the carbon filament may be a carbon nanotube. As the carbon nanotube exhibits satisfactory conductivity (or has a low electrical resistance value), the carbon wire can have a further reduced electrical resistance value.
- In the above carbon wire, the graphite layer may be a carbon nanotube. The graphite layer can also act as an electrically conductive layer, and can thus more effectively reduce the carbon wire's electrical resistance.
- According to a reference example, a wire assembly includes a plurality of the above carbon wires. This allows the wire assembly to be sufficiently low in resistance. Furthermore, the plurality of carbon wires assembly to have a large area in cross section and accordingly enable the wire assembly to pass a current of a large value.
- According to the present invention, a method of producing a carbon wire includes the steps of: preparing an assembly portion formed of a plurality of carbon
filaments in contact with one another, and exposing a surface of the assembly portion to liquid gallium to provide a graphite layer on the surface of the assembly portion. - This allows an assembly portion at a portion of carbon filament that is exposed at a surface to be exposed to liquid gallium to provide a graphite layer through the liquid gallium's catalysis. When this is compared for example with providing a graphite layer directly on a surface of the assembly portion through vapor deposition, the former allows a process to be performed at a temperature lower than the latter to provide the graphite layer to obtain the present carbon wire
- In the above method of producing a carbon wire, the step of exposing may be performed with compressive stress exerted to the assembly portion. This allows a graphite layer to be provided while compressive stress is exerted to the assembly portion, and the resultant carbon wire can have the assembly portion configured of carbon filaments in contact with one another over an increased area with increased pressure exerted to that area, This more reliably ensures that the carbon wire has a reduced electrical resistance value.
- In the above method of producing a carbon wire, the step of exposing may be performed with liquid gallium compressed to exert compressive stress to the assembly portion. The liquid gallium compressed (for example by increasing the pressure of an ambient gas that is brought into contact with the liquid gallium, or by enclosing Ga and CNTs in a capsule or a similar container and then compressing them together with the capsule (or container) can facilitate exerting compressive stress to the assembly portion.
- In the above method of producing a carbon wire, the step of exposing may be performed with the liquid gallium in contact with ambient gas regulated in pressure to compress the liquid gallium, This can facilitate compressing the liquid gallium. Furthermore, regulating the ambient gas's pressure can facilitate regulating the value of the pressure applied to the liquid gallium,
- In the above method of producing a carbon wire, the step of exposing is performed with the liquid gallium having a temperature in a range of 450°C-750°C. This can more efficiently cause the liquid gallium's catalytic reaction providing the graphite layer from an outer circumference of the assembly portion. Note that the liquid gallium's lower temperature limit is set at 450°C because if the liquid gallium has a temperature lower than that temperature, the liquid gallium's catalytic reaction is insufficiently provided. Furthermore, the liquid gallium's upper temperature limit is set at 750°C in order to prevent the assembly portion from having its constituent carbon filaments decomposed.
- The above method of producing a carbon wire may include, before the step of exposing, the step of providing an amorphous carbon layer as a surface layer of the assembly portion. Previously providing the amorphous carbon layer that is to serve as the graphite layer allows the graphite layer to be provided while in the assembly portion the carbon filaments' structure can be maintained. This allows an increased degree of freedom in designing the carbon wire in configuration.
- The above method of producing a carbon wire may further include, after the step of exposing, the step of removing gallium adhering to a surface of the carbon wire. The step of exposing may results in the carbon wire having a surface with the liquid gallium solidified and thus adhering thereto. The step of removing can remove such solidified gallium from the surface of the carbon wire.
- According to the present invention, a method of producing a wire assembly includes the step of: producing a plurality of carbon wires in the above method of producing carbon wire; and stranding the plurality of carbon wire together to form a wire assembly. Low-resistance carbon wires according to the present invention can thus be used to produce a wire assembly.
- Furthermore, a reference example provides electrically conductive film having a carbon nanotube network formed of a plurality of carbon nanotubes linked together by graphite film.
- The present invention provides a method of producing the electrically conductive film having a carbon nanotube network formed of a plurality of carbon nanotubes linked together by graphite film, including the step of exposing a carbon nanotube network to Ga vapor to provide
the graphite film. Bulk Ga and carbon as seen in phase diagram are of a non solid solution type. However, the present inventors have found that in a microscale, Ga and carbon at their surfaces have a bond caused and Ga vapor per se has a catalysis for graphitization reaction. - The present invention provides a method of producing the electrically conductive film according to
claim 10. The present inventors have found that Ga not only in the form of an aggregation of atoms as liquid but also in the form of vapor having atoms liberated converts to a graphite structure at a surface of amorphous carbon, i.e., that it causes a graphitization reaction of the surface of amorphous carbon. In other words, the present invention includes the step of causing Ga vapor to act on amorphous carbon or a similar carbon source to graphitize its surface. Note that in the present invention that graphite film includes both a graphene film in the form of a single layer, and a graphite film formed of graphene films stacked in a plurality of layers. - According to the present invention, the method of producing the electrically conductive film preferably includes, before the step of exposing, the step of mechanically pressure-welding those portions of a plurality of carbon nanotubes forming the carbon nanotube network which are in contact with one another.
- A reference example provides an electrically conductive substrate formed with a substrate and electrically conductive film provided on the substrate and having a carbon nanotube network formed of a plurality of carbon nanotubes linked together by graphite film.
- The present invention provides a method of producing an electrically conductive substrate, according to
claim 12. - The present invention provides a method of producing the electrically conductive substrate according to
claim 13. - According to the present invention, the method of producing the electrically conductive substrate preferably includes, before the step of exposing, the step of mechanically pressure-welding those portions of a plurality of carbon nanotubes forming the carbon nanotube network which are in contact with one another.
- A reference example provides a transparent, electrically conductive sheet formed with a sheet of resin and electrically conductive film provided on the sheet of resin and having a carbon nanotube network formed of a plurality of carbon nanotubes linked together by graphite film.
- Preferably in the transparent, electrically conductive sheet, a surface of the sheet of resin that has the electrically conductive film is formed of one of thermosetting resin and ultraviolet (UV) curable resin.
- The present invention provides a method of producing the transparent, electrically conductive sheet according to claim 15.
- The present invention provides a method of producing the transparent, electrically conductive sheet according to
claim 16. - According to the present invention, the method of producing a transparent, electrically conductive sheet preferably includes, before the step of exposing, the step of mechanically pressure-welding those portions of the plurality of carbon nanotubes forming the carbon nanotube network which are in contact with one another.
- According to the present invention, preferably, the method of producing a transparent, electrically conductive sheet includes the step of transferring to transfer the electrically conductive film to the surface of the sheet of resin that is formed of one of thermosetting resin and ultraviolet curable resin, and the method further includes the step of setting/curing one of the thermosetting resin and the ultraviolet curable resin.
- Furthermore, a reference example provides a method of producing graphite film by exposing a surface of a carbon source to Ga vapor to provide graphite film on the surface of the carbon source.
- Preferably, the Ga vapor has a temperature equal to or higher than 600°C. Ga vapor having a temperature of 600°C or higher allows graphitization reaction to proceed satisfactorily.
- Preferably, the Ga vapor has a uniform vapor pressure at the surface of the carbon source. This allows a graphite film to be provided with a homogenous property.
- Preferably, the Ga vapor is plasmatized.
- Furthermore, preferably, the carbon source is located on a substrate and the Ga vapor plasmatized is brought into contact with the substrate having a temperature equal to or higher than 400°C.
- Ga vapor plasmatized allows graphite film to be provided while the substrate having a source material of amorphous carbon applied thereon is maintained at as low a temperature as approximately 400°C. Semiconductor device processes require significantly strict temperature restrictions in order to maintain impurity profiles of channels, source/drain layers and the like. For example, approximately 500°C or higher temperatures cannot be set for processing. Plasmatized gallium allows catalysis
to be exhibited at a temperature equal to or lower than 400°C. - Preferably, the carbon source is amorphous carbon.
- Preferably, the amorphous carbon is amorphous carbon film provided on a monocrystalline substrate formed of one type selected from the group consisting of SiC. Ni, Fe, Mo, and Pt.
- For example, when a graphite film is provided on a silicon oxide film, the graphite film is not necessarily provided as monocrystalline film and instead as polycrystalline film having a domain structure in a broad sense. An underlying substrate that is a SiC, Ni, Fe, Mo, Pt or similar crystalline substrate allows graphite film to be provided as monocrystalline film.
- Preferably, the carbon source is a hydrocarbon material. In the present invention the carbon source other than amorphous carbon may be used, such as phenanthrene, pyrene, camphor or similar hydrocarbon materials.
- In the method of producing graphite film, the carbon source can be a three dimensional amorphous carbon structure having a surface exposed to Ga vapor to provide graphite film having a three dimensional surface structure.
- For example, Ga vapor used as a catalyst can graphitize not only amorphous carbon in the form of a plane but also a surface of a pillar or a similar, three dimensional, any spatial geometry of amorphous carbon.
- Furthermore, a reference example relates to a method of producing graphite film by mixing Ga vapor and a source material gas of a carbon source together and supplying a mixture thereof to provide graphite film on a substrate. This allows the substrate to have relatively thick graphite film thereon.
- Preferably, the Ga vapor has a temperature equal to or higher than 600°C or higher.
- Preferably, the Ga vapor is plasmatized.
- Preferably, the Ga vapor plasmatized is brought into contact with the substrate having a temperature equal to or higher than 400°C.
- The present invention can achieve a low resistance carbon wire and a low resistance wire assembly.
- Furthermore, the present invention can achieve a low resistance electrically conductive film having a carbon nanotube network, and an electrically conductive substrate and a transparent, electrically conductive sheet utilizing the same;
- The present invention also has a side effect including large light transmission. If fine particles or the like are used to provide a surface of a substrate with electrical conductivity, the particles must be closely packed to cover the surface of the substrate entirely. In contrast, carbon nanotubes can eliminate the necessity of covering the surface of the substrate entirely. The carbon nanotubes that do not entirely cover the surface of the substrate allow the substrate to have the surface with many gaps, which can facilitate transmitting light.
- Furthermore, the present method of producing graphite film is applicable to producing a transparent, electrically conductive sheet used for a variety of electronic devices, large-size displays and the like. The present invention, for device applications, can facilitate efficient mass production of monocrystalline graphite film. Furthermore, the present invention, for transparent, electrically conductive sheet, can provide means for obtaining a large area and number of layers of graphite film
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Fig. 1 is a schematic cross section showing an embodiment of a carbon wire in the present invention, -
Fig. 2 is a schematic cross section taken along a line II-II shown inFig. 1 . -
Fig. 3 is a schematic cross section showing an embodiment of a wire assembly in the present invention. -
Fig. 4 is a flowchart for illustrating a method of producing theFig. 3 wire assembly. -
Fig. 5 is a flowchart for illustrating another method of producing a wire assembly according to the present invention. -
Fig. 6 is a schematic diagram for illustrating a coating step shown inFig. 5 -
Fig. 7 is a schematic diagram for illustrating a Ga catalyst reaction step shown inFig. 5 . -
Fig. 8 schematically shows a process for producing electrically conductive film, an electrically conductive substrate, and a transparent, electrically conductive sheet according to the present invention. -
Fig. 9 is a schematic cross section of one example of a graphite film production apparatus used in the present invention. -
Fig. 10 is a schematic cross action of one example of a graphite film production apparatus used in the present invention. -
Fig. 11 is a schematic cross section of one example of a graphite film production apparatus showing a configuration of a subordinate Ga reaction chamber. -
Fig. 12 is a schematic cross section of one example of a graphite film production apparatus employing Ga plasma. -
Fig. 13 is a schematic cross section of one example of a graphite film production apparatus with a carbon material supply system and a Ga supply system separated for forming a large area of transparent, electrically conductive sheet. - Hereinafter reference will be made to the drawings to describe the present invention in an embodiment. In the figures, identical or corresponding components are identically denoted and will not be described repeatedly in detail.
-
Fig. 1 is a schematic cross section showing an embodiment of a carbon wire in the present invention.Fig. 2 is a schematic cross section taken along a line II-II shown inFig. 1 . With reference toFig, 1 and Fig. 2 , the present invention provides a carbon wire 1, as will be described hereinafter. Note thatFig. 1 shows carbon wire 1 in cross section as seen in a direction perpendicular to its longitudinal direction andFig. 2 shows carbon wire 1 in cross section as seen in a direction along its longitudinal direction. - As shown in
Fig. 1 and Fig. 2 , carbon wire 1 includes anassembly portion 3 and a graphite layer 4.Assembly portion 3 is configured of a plurality of carbon filaments implemented ascarbon nanotubes 2 in contact with one another. Graphite layer 4 surroundsassembly portion 3. WhileFig. 1 and Fig. 2 show carbon wire 1 configured, as seen in cross section, of twocarbon nanotubes 2, carbon wire 1 may haveassembly portion 3 configured, as seen in cross section, of two or more, e.g., three or four carbon nanotubes (CNTs) 2. Furthermore, as shown inFig. 1 and Fig. 2 ,assembly portion 3 is configured ofcarbon nanotubes 2 in contact with one another. Furthermore, as shown inFig. 2 , carbon wire 1 as seen in its longitudinal direction also hascarbon nanotubes 2 successively in contact with one another to allowassembly portion 3 to havecarbon nanotubes 2 forming an electrically conducting path extending in the longitudinal direction of carbon wire 1 and capable of passing an electric current therethrough. - Carbon wire 1 can thus have an outer circumference formed of graphite layer 4. holding
assembly portion 3 to ensure thatassembly portion 3 hascarbon nanotubes 2 in contact with one another. This allowsassembly portion 3 to havecarbon nanotubes 2 in contact with one another over an increased area with increased pressure exerted to that area. This can preventassembly portion 3 from havingcarbon nanotubes 2 in contact with one another insufficiently and hence carbon wire 1 from having an increased electrical resistance value. Furthermore, graphite layer 4 can also act as an electrically conductive layer allowing carbon wire 1 to have a further reduced electrical resistance value. - Furthermore, carbon wire 1 including
assembly portion 3 configured of carbon filaments formed of satisfactorily electricallyconductive carbon nanotubes 2 ensures that carbon wire 1 has a reduced electrical resistance value. - Preferably, carbon wire 1 has graphite layer 4 formed of a carbon nanotube. In that case, graphite layer 4 can also act as an electrically conductive layer, and carbon wire 1 can further be reduced in electrical resistance.
- Furthermore, preferably, graphite layer 4 causes
carbon nanotubes 2 that configureassembly portion 3 to press one another. This allowsassembly portion 3 to havecarbon nanotubes 2 in contact with one another over an increased area with increased pressure exerted to that area, and also allows graphite layer 4 to contactcarbon nanotubes 2 ofassembly portion 3 over an increased area with increased pressure exerted to that area. As a result, carbon wire 1 of low resistance can be implemented. -
Fig. 3 is a schematic cross section showing an embodiment of a wire assembly in the present invention. With reference toFig. 3 , the present invention provides a wire assembly 5, as will be described hereinafter. Note thatFig. 3 shows wire assembly 5 in cross section as seen in a direction perpendicular to its longitudinal direction. - With reference to
Fig. 3 , wire assembly 5 includes a plurality of carbon wires 1 as described above (inFig. 3 , it includes seven carbon wires 1). Thus, carbon wire 1 of low resistance produced according to the method of the present invention can be used to implement wire assembly 5 of sufficiently low resistance. Furthermore, using a plurality of carbon wires 1 allows wire assembly 5 to have a large area in cross section and hence pass a current having a large value. Furthermore, wire assembly 5 may have a plurality of carbon wires 1 twined together, or simply bundied and bound by a clamping member surrounding the plurality of carbon wires 1. The clamping member may for example be an annular clamp formed for example of insulator (e.g., resin). - Note that wire assembly 5 may be configured of carbon wires 1 different in number than as shown in
Fig. 3 (for example, the wire assembly may be configured of two or any larger number of carbon wires). Furthermore, whileFig. 3 shows wire assembly 5 configured of carbon wires 1 all identically structured, carbon wire 1 may be different in configuration for some portion in cross section of wire assembly 5. For example, wire assembly 5 as seen in cross section may have a center portion with carbon wire 1 configured of carbon nanotubes 2 (seeFig. 1 ) bundled in an increased number (as seen in a cross section in a direction perpendicular to that in which carbon wire 1
extends) (e.g., 10 or more carbon nanotubes 2), while wire assembly 5 as seen in cross section may have an outer circumference with carbon wire 1 configured ofcarbon nanotubes 2 bundled in a number smaller than that ofcarbon nanotubes 2 bundled that are located in carbon wire 1 at the center portion (e.g., less than ten, more specifically, five orless carbon nanotubes 2 may be bundled together). - Furthermore, wire assembly 5 may be exposed to liquid gallium (a Ga catalyst), as done in the step of providing graphite layer 4 for carbon wire 1, as will be described hereinafter, to provide a graphite layer surrounding wire assembly 5. Furthermore, a plurality of wire assemblies 5 each externally circumferentially surrounded by the graphite layer are prepared and bundled together to prepare a wire having a larger area in cross section. Furthermore, the wire is also exposed to liquid gallium to have a graphite layer surrounding the wire. Furthermore, a plurality of such wires each externally circumferentially surrounded by the graphite layer are bundled together to configure a wire having a larger area in cross section. Thus bundling wires together to provide a wire assembly, exposing the wire assembly to liquid gallium to provide a graphite layer on a surface of the wire assembly, and further bundling a plurality of such wire assemblies each having the graphite layer provided thereon are repeated to produce a wire assembly further reduced in resistance and increased in diameter.
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Fig. 4 is a flowchart for illustrating a method of producing theFig. 3 wire assembly. With reference toFig. 4 , theFig. 3 wire assembly is produced in the method, as will be described hereinafter. - As shown in
Fig. 4 , wire assembly 5 is produced in a method in which a CNT production step (S10) is first performed. In this CNT (carbon nanotube) production step (S10) a short (e.g., several µm long) carbon nanotube is production in a conventionally well known method. - For example, a substrate used to produce a CNT is provided on a surface thereof with an underlying film, and on the underlying film a plurality of nanoparticles acting as a catalyst for forming a carbon nanotube are formed such that they are dispersed. The underlying, film is configured of material preferably for example of alumina, silica, sodium aluminate, alum, aluminum phosphate or a similar aluminum compound, calcium oxide, calcium carbonate, calcium sulfate or a similar calcium compound, magnesium oxide, magnesium hydroxide, magnesium sulfate or a similar magnesium compound, or calcium phosphate, magnesium phosphate or a similar apatite material. The nanoparticles can be configured of activated metal, such as vanadium (V), chromium (Cr), manganese (Mn), iron (Fe), cobalt (Co), nickel (Ni), copper (Cu), zinc (Zn) or the like.
- Furthermore, the nanoparticles have a size for example equal to or smaller than 100 nm, preferably 0.5 nm-10 nm, more preferably 1.0 nm-5 nm. Furthermore, the underlying film can have a thickness for example of 2.0 nm-100 nm.
- A gas of a source material for forming a carbon nanotube is supplied to a surface of the substrate having the nanoparticles formed thereon, and the substrate is heated in that condition As a result, a carbon nanotube is grown on the surfaces of the nanoparticles disposed on the surface of the substrate. The carbon nanotube thus grown is used to form an assembly portion configured of a plurality of carbon nanotubes assembled together, as will be described hereinafter.
- Subsequently, as shewn in
Fig. 4 , a CNT assembly formation step (S20) is performed. In this step (S20), a conventionally well known method is used to strand a plurality of carbon nanotubes that are produced in the step (S10) together to form an assembly portion formed of the carbon nanotubes. In this step (S20), a conventionally well known method can be used to form the assembly portion of the carbon nanotubes For example, a required number of nano-size catalysts can be adjacently placed to grow carbon nanotubes (CNTs) to bond a required number of CNTs together, or furthermore, a plurality of CNTs may have their ends chucked and rotated, and thus formed into a stranded wire. - Subsequently, a Ga catalyst reaction step (S30) is performed. In this step (S30), the assembly portion formed of the carbon nanotubes in the step (S20) has a surface exposed to liquid gallium (Ga). As a result, the a portion formed of the carbon nanotubes has a surface layer converted by the liquid gallium's catalytic reaction to a graphite layer surrounding the assembly portion. As a result, as shown in
Fig. 1 and Fig. 2 , carbon wire 1 havingassembly portion 3 grounded by graphite layer 4 can be obtained. In other words, the steps (S10) to (S30) correspond to a method of producing carbon wire 1. - In doing so, the liquid gallium has a temperature of 450°C-750°C more preferably 550°C-700°C. This can more efficiently cause the liquid gallium's catalytic reaction forming the graphite layer at an outer circumference of
assembly portion 3. - Furthermore, the step (S30) of exposing a surface of the assembly portion to liquid gallium to provide a graphite layer is preferably performed while compressive stress is exerted to
assembly portion 3. Providing graphite layer 4 whileassembly portion 3 experiences compressive stress allows carbon wire 1 to be formed withassembly portion 3 configured ofcarbon nanotubes 2 in contact with one another over an increased area with increased pressure exerted to that area. This further ensures that carbon wire 1 and wire assembly 5 achieve a reduced electrical resistance value. - Furthermore in the step (S30) preferably the liquid gallium is compressed to exert compressive stress to
assembly portion 3, More specifically, an ambient gas that contacts the liquid gallium may be regulated in pressure to compress the liquid gallium. For example, the liquid gallium may be held in a bath held in a holding container (a chamber) and an ambient gas (that contacts the liquid gallium) in that chamber may be regulated in pressure. The liquid gallium thus compressed can facilitate exerting compressive stress toassembly portion 3. Furthermore, the ambient gas regulated in pressure can facilitate regulating a value in pressure applied to the liquid gallium. Note that the ambient gas can for example be argon gas, nitrogen gas or an inert gas less reactable with carbon nanotube and liquid gallium. Furthermore, the ambient gas's pressure can be set for example at gallium (Ga) vapor pressure to 10 Mpa, more preferably 1 × 10-5 torr to 1 Mpa. - Subsequently, an adhering-Ga removal step (S40) is performed. More specifically, after the graphite layer is provided, i.e., after the step (S30) is performed, carbon wire 1 has removed the gallium adhering on its surface, i.e., the adhering-Ga removal step (S40) is performed to remove gallium adhering to a surface of carbon wire 1 (i.e., a surface of graphite layer 4) provided. The gallium can be removed in any method. For example, a solution (e.g., diluted hydrochloric acid or diluted nitric acid) that can dissolve gallium may be sprayed to carbon wire 1, or a bath of the solution can be used to immerse carbon wire 1 therein. This can remove from a surface of carbon wire 1 the gallium solidified and thus adhering to the surface of carbon wire 1 in the step (S30). This can reduce in a post-step, or a processing step (S50), a possibility that otherwise solidified gallium causes a defect in forming wire assembly 5.
- The steps (S10) to (S40) are performed a plurality of times or the step (S20) is performed to form a plurality of assembly portions formed of carbon nanotubes and the plurality of sombly portions concurrently and in parallel undergo the step (S30) and the step (S40) to obtain a plurality of carbon wires. Thus the step (S10) to (S40) indicating a method of producing a carbon wire are used to perform a process for producing a plurality of carbon wires.
- Subsequently, the processing step (S50) is peformed to strand a plurality of carbon wires 1 that are obtained through the step (S10) to the step (S48) together to form wire assembly 5 (see
Fig. 3 ). In this step (S50), any conventionally well known method can be employed to strand the plurality ofcarbon wires 1 together. For example, a required number of nano-size catalyst can be adjacently placed to grow CNTs to bond a required number of CNTs together, or furthermore, a plurality of CNTs may have their ends chucked and rotated, and thus formed into a stranded wire Wire assembly 5 formed of carbon wires 1, as shown inFig. 3 , and low in resistance, can thus be obtained. - The method of producing carbon wire 1 or wire assembly 5, as described above, allows a portion of a carbon nanotube(s) of
assembly portion 3 that is exposed at a surface to be exposed to liquid gallium to obtain graphite layer 4 through the liquid gallium's catalysis (seefig. 1 and Fig. 2 ), as has been described in the step (S30). When this is compared for example with providing graphite layer 4 directly on a surface ofassembly portion 3 through vapor deposition, the former allows a process to be performed at a temperature lower than the latter to provide graphite layer 4 to provide the present carbon wire. -
Fig 5 is a. flowchart for illustrating another method of producing a wire assembly according to the preset invention.Fig. 6 is a schematic diagram for illustrating a coating step shown inFig. 5 .Fig. 7 is a schematic diagram for illustrating a Ga catalyst ration step shown inFig. 5 . With reference toFig. 5 to Fig. 7 , the present invention provides the wire assembly produced in the other method, as will be described hereinafter. - The
Fig. 5 wire assembly production method includes steps basically similar to those of theFig. 4 wire assembly production method, except that the former has the Ga catalyst reaction step (S30) preceded by the step of providing an amorphous carbon layer as a surface layer of an assembly portion, i.e., a coating step (S60). - More specifically, in the
Fig. 5 wire assembly production method, the step (S10) and the step (S20) are initially performed, as done in theFig. 4 wire assembly production method, and thereafter, as shown inFig. 6 , on a surface ofassembly portion 3 obtained, anamorphous carbon layer 11, which is to serve as graphite layer 4(seeFig. 7 ), is provided.Amorphous carbon layer 11 can be provided in any conventional well known method. For example, phenanthrene (C14H10), pyrene, methane acetylene or the like may be thermally decomposed to provideamorphous carbon layer 11, or an electron beam or an ion beam may be used to decompose a hydrocarbon based gas. As a result, theFig. 6 structure is obtained. - Subsequently, as shown in
Fig. 5 , the Ga catalyst reaction step (S30) is performed, This step (S30) can be performed in a method basically similar to the step (S30) performed in theFig 4 production method. It should be noted, however, that in theFig. 5 step (S30),amorphous carbon layer 11 has a surface layer converted to graphite layer 4 through the liquid gallium's catalytic reaction. As a result, carbon wire 1 having a structure shown inFig. 7 can be obtained. - The
Fig. 5 production method can thus provide graphite layer 4 fromamorphous carbon layer 11 while maintaining a structure ofcarbon nanotubes 2 inassembly portion 3. The method thus allows an increased degree of freedom in designing carbon wire 1 in configuration. - Subsequently, as done in the
Fig. 4 production method, the step (S40) and the step (S50) can be performed to obtain a wire assembly similar in structure to theFig. 3 wire assembly 5. Note that theFig 5 production method produces a wire assembly configured of carbon wire 1 havingamorphous carbon layer 11 posed betweencarbon nanotube 2configuring assembly portion 3 and graphite layer 4, as can be seen inFig. 7 . -
Fig. 8 schematically shows a process for producing electrically conductive film, an electrically conductive substrate, and a transparent, electrically conductive sheet according to the present invention. Initially, as shown inFig. 8 (a) , a substrate 17 is exposed to a slurry having carbon nanotubes (hereinafter referred to as CNT(s)) 2 dispersed therein to form a carbon nanotube network (hereinafter referred to as a CNT network) formed of a plurality of CNTs. The carbon nanotube network has a surface exposed to Ga vapor to allow the CNT network to have its constituent CNTs linked together by graphite film to obtain electricallyconductive film 18 and an electrically Conductive substrate (Fig. 8 (b) ). Furthermore, a resin sheet is brought into contact, at a surface thereof having thermosestting resin or ultraviolet (UV) curable resin thereon, with the surface of electricallyconductive film 18 that has the CNT network formed thereon, and the resin sheet is then thermally set or UV-cured to transfer the CNT network to the resin sheet to obtain the present transparent, electrically conductive sheet (Fig. 8 (c) ). -
Carbon nanotube 2, which is a tube having a lattice structure or carbocyclic six-membered rings, may be a tube structured of a single sheet, i.e., a single-walled carbon nanotube (hereinafter also referred to as "SWNT"), or may be a. tube structured of multiple layers of tubes having the lattice structure of carbocyclic six-membered rings, i.e., a multiwalled-carbon nanotube (hereinafter also referred to as "MWNT"). In general, an SWNT is more flexible. An MWNT is less flexible than the SWNT, and MWNTs having more multiple layers have a tendency to be more rigid. It is desirable that an SWNT of an MWNT be used depending on the purpose, as occasion demands, with their properties considered. - In what length the carbon nanotube is applicable is not limited to any particular value. In general, however, a carbon nanotube in a range of 10 nm to 1000 µm, preferably 100 nm to 100 µm, is used. The carbon nanotube is not limited in diameter (or thickness) to any particular value. In general, however, a carbon nanotube in a range of 1 nm to 50 nm is used, and for an application requiring more transparency, a carbon nanotube in a range of 3 mn to 10 nm is preferably used.
- Note that when carbon nanotubes are applied to substrate 17, it is preferable to previously prepare a slurry having the CNTs dispersed therein. The slurry is prepared as follows CNTs prepared in an are process are introduced in acetone and bundled CNTs are ultrasonically debundled and dispersed uniformly in the acetone Subsequently, before time elapses, the slurry is sprayed to substrate 17 and dried to form a CNT network on the substrate. The acetone may be replaced with alkyl benzene sulfonate or a similar surfactant, a sulfosuccinate diester or a similar solvent having a structure of a hydrophobic moiety-a hydrophilic moiety-a hydrophobic moiety to be used to similarly disperse CNTs therein. In that case, a dispersant or the like will enter between those portions of CNTs at which the CNTs contact one another. Accordingly, preferably, after the slurry is dried on the substrate, water or acetone is used to wash away the dispersant or other matters adhering to the substrate
- A carbon nanotube network is formed of a plurality of CNTs randomly intertwined with one another on substrate 17 and thus formed in a network. A conventional CNT network is large in electrical resistance, as it has its CNTs electrically connected only by the physical contact made at those portions of the CNTs at which the CNTs contact one another. The present invention allows a CNT network to be processed with Ga vapor to provide CNTs with a graphite film on their surfaces to link the CNTs together. This can reduce the CNT network's electrical resistance and thus provide electrically conductive film having a low resistance value.
- CNTs may be brought into contact with a substrate to form a CNT network in any method. They may be applied in any of generally used methods. Applicable methods include spin-coating, dip-coating, curtain-coating, roll-coating, applying with a brush, spray-coating and the like, for example. In particular, spin-coating is preferable, as it can easily provide a CNT network in a homogeneous thin film.
- Substrate 17 may be any substrate that is normally used for production of electrically conductive film. For example, a substrate formed of glass, mica, quartz or a similar transparent material allows an electrically conductive substrate as a whole to have significantly increased transparency. While it is known to employ carbon vapor deposition, meta vapor deposition or the like to provide a surface of a substrate with electrical conductance, employing a carbon nanotube network to provide a surface of substrate 17 with electrical conductance, as described in the present invention, can eliminate the necessity of completely covering the surface with carbon nanotube The network has gaps, and thus allows an electrically conductive substrate to have significantly high optical transmittance for a predetermined surface conductivity.
- Electrically
conductive film 18 produced according to the method of the present invention is electrically conductive film having a carbon nanotube network formed of a plurality of carbon
nanotubes linked together by graphite film. The electrically conductive film has the CNTs electrically connected via the graphite film, and thus has a low resistance value characteristically. - The electrically conductive substrate produced according to the method of the present invention is an electrically conductive substrate formed of substrate 17 and electrically
conductive film 18 provided on substrate 17 and having a carbon nanotube network formed of a plurality of carbon nanotubes linked together by graphite film. The electrically conductive substrate has CNTs thereon electrically connected via the graphite film, and thus has a low resistance value characteristically. - Resin sheet 4 may be of any highly transparent resin that is normally used as a substrate. Preferably, polymeric (PET) film having epoxy resin or similar thermosetting resin, or acrylic syrup or similar UV curable resin or similar curable resin applied thereon is used, as it allows the CNT network formed on the electrically conductive film to be transferred efficiently.
- The method of producing electrically conductive film, an electrically conductive substrate and a transparent, electrically conductive sheet in accordance with the present invention will more specifically be described hereinafter for the step of providing graphite film on a CNT network.
-
Fig. 9 is a schematic cross section of one example of a graphite film production apparatus used in the present invention. - The present invention employs a graphite film production apparatus configured of a quartz reaction tube 6 and an
alumina container 20 provided in quartz reaction tube 6 and having liquid Ga 9 introduced therein. Substrate 17 with a plurality ofcarbon nanotubes 2 formed thereon in a CNT network is to be processed, placed in a vicinity ofalumina container 20. External to quartz reaction tube 6, a heater 7 is provided for the reaction tube to regulase the internal temperature of quartz reaction tube 6. - Substrate 17 may be a conventionally well known substrate that is normally used for production of electrically conductive film. However, a substrate formed of glass, mica, quartz or a similar transparent material allows an electrically conductive film as a whole to have significantly increased transparency.
- The CNT network formed of a
plurality carbon nanotubes 2 may be formed in any convention well known method. For example the methos includes spin-coating, dip-coating, curtain-coating, roll-coating, applying with a brush, spray-coating and the like, for example. In particular, spin-coating is preferable, as it can easily provide a CNT network in a homogeneous thin film. Subsequently, preferably, this substrate is washed to prevent the CNT network from having a dispersant or similar impurity remaining therein. - To bring the CNTs into close contact with one another, a roller or the like is preferably used to firmly compress the CNT network from above.
- Furthermore, preferably, amorphous carbon film is provided on the CNT network to ensure that graphite film is provided. The amorphous carbon film may be provided in any conventional well known method. For example, phenanthrene (C14H10). pyrene, methane acetylene or the like may be thermally decomposed to provide the amorphous carbon film, or an electron beam or an ion beam may be used to decompose a hydrocarbon based gas. The amorphous carbon film preferably has a thickness equal to or smaller than 10 nm, as such film can enhance transparency.
- Initially, a substrate to be processed, as aforementioned, is secured in quartz reaction tube 6 horizontally, and a turbo pump is used to vacuum the background to 10-6 Torr or lower.
- Heater 7 heats the reaction tube to evaporate liquid Ga 9 in quartz reaction tube 6 and beats Ga vapor 5 to 600°C or higher to bring the vapor into contact with a surface of the CNT network formed of a plurality of
carbon nanotubes 2, More preferably, Ga vapor 5 is heated to 800°C or higher to enhance the catalysis of Ga vapor 5. - The above heat treatment is conducted for 10 minutes to 1 hour, and subsequently the reaction tube is slowly cooled to again attain room temperature.
- The heat treatment in Ga vapor 5 provides graphite film on a surface of the CNT network formed of
carbon nanotubes 2. Thus, on substrate 17, electrically conductive film having a carbon nanotube network formed of a plurality of carbon nanotubes linked together by graphite film is provided, and an electrically conductive substrate is thus obtained. - The electrically inductive film produced in the aforementioned process is used to produce a transparent, electrically conductive sheet in a method, as will be described hereinafter.
- A sheet of resin is brought into contact with that surface of the aforementioned electrically conductive substrate which has the CNT network formed thereon to transfer the CNT network to the sheet of resin. Preferably, thermosetting resin or UV curable resin is applied to that surface of the sheet of resin which is bought into contact with the CNT network. Subsequently, the sheet of resin is set/cured to secure the CNT network to the sheet of resin to produce a transparent, electrically conductive sheet.
-
Fig. 10 is a schematic cross section of one example of a graphite film production apparatus used in the present invention. - The present invention employs a graphite film production apparatus configured of quartz reaction tube 6 and
alumina container 20 provided in quartz reaction tube 6 and having liquid Ga 1 introduced therein. Substrate 17 withamorphous carbon film 21 provided thereon is to be processed, placed in a vicinity ofalumina container 20. External to quarts reaction tube 6, heater 7 is provided for the reaction tube to regulate the internal temperature of quartz reaction tube 6. - Substrate 17 may be a conventionally well known substrate that is used as a substrate for production of electrically conductive film. Preferably, an SiC, Ni, Fe, Mo, Pt or similar, monocrystalline substrate is used, as monocrystalline graphite film can be obtained.
-
Amorphous carbon film 21 may be provided in any conventional well known method. For example, phenanthrene (C14H10), pyrene, methane acetylene or the like may be thermally decompose to provideamorphous carbon film 2, or an electron beam or an ion beam may be used to decompose a hydrocarbon based gas.Amorphous carbon film 21 preferably has a thickness set to match that of graphene film or graphite film targeted. - Initially, a substrate to be processed, as aforementioned, is secured in quartz reaction tube 6 horizontally, and a turbo pump is used to vacuum the background to 10-6 Torr or lower.
- Heater 7 heats the reaction tube to evaporate liquid Ga 9 in quartz reaction tube 6 and heats Ga vapor 5 to 600°C or higher to bring the vapor into contact with a surface of
amorphous carbon film 21. - The above heat treatment is conducted for 10 minutes to 1 hour, and subsequently the reaction tube is slowly cooled to again attain room temperature.
- The beat treatment in Ga vapor 5 provides graphite film on a surface of
amorphous carbon film 21. -
Fig. 11 is a schematic cross section of one example of a graphite film production apparatus used in the present invention when Ga vapor has unifom vapor pressure at a surface of a carbon source. A second embodiment employs a graphite film production apparatus having quartz reaction tube 6 and a subordinateGa reaction chamber 22 provided in quartz reaction tube 6 andaccommodating alumina container 20 having liquid Ga 9 introduced therein, and substrate 17 havingamorphous carbon film 21 thereon, i.e., a substrate to be processed. SubordinateGa reaction chamber 22 has a wall having a differential evacuation in the form of a small gap. - The first embodiment shows a graphite film production apparatus having quartz reaction tube 6 internally filled with Ga vapor 5 generated from liquid Ga 9. However, while a portion of quartz reaction tube 6 that is close to heater 7 is maintained at a predetermined high temperature, portions of quartz reaction tube 6 that are remoter from heater 7 are lower in temperature, and some of them have room temperature. Thus, in quartz reaction tube 6, Ga vapor 5 varies in temperature at different locations and thus does not have uniform vapor pressure.
- As shown in
Fig. 11 , quartz reaction tube 6 that has subordinateGa reaction chamber 22 therein allows Ga vapor 5 to be held in subordinateGa reaction chamber 22 and thus have a fixed vapor pressure. Furthermore, subordinateGa reaction chamber 22 that accommodates thereinalumina container 20 having liquid Ga 9 introduced therein, and substrate 17 havingamorphous carbon film 21 thereon, or a substrate to be processed, and that is vacuumed through a small gap serving as a differential evacuation port, can internally have a Ga vapor pressure of a possible maximal value and also provide a uniform Ga vapor pressure in a vicinity of the substrate to be processed. The aforementioned production method can provide graphite film having a surface without inconsistency in color or roughness and thus having a significantly smooth mirror surface. - Initially, a substrate to be processed, as aforementioned, is secured in quartz reaction tube 6 horizontally, and a turbo pump is used to vacuum the background to 10-6 Torr or lower.
- Heater 7 heats the reaction tube to evaporate liquid Ga 9 in quartz reaction tube 6 and heats Ga vapor 5 to 600°C or higher to bring the vapor into contact with a surface of
amorphous carbon film 21. More preferably, Ga vapor 5 is heated to 800°C or higher to enhance the catalysis of Ga vapor .5. - The heat treatment in Ga vapor 5 provides graphite film on a surface of
amorphous carbon film 21. -
Fig. 12 is a schematic cross section of one example of a graphite film production apparatus employed in the present invention with Ga vapor plasmatized. A third embodiment employs a graphite film production apparatus having quartz reaction tube 6accommodating alumina container 20 having liquid Ga 9 introduced therein, and aplasma producing electrode 10, with aheater 12 provided at the alumina container for Ga. Substrate 17 withamorphous carbon film 21 thereon, or a substrate to be processed, is positioned in a vicinity ofalumina container 20 between pairedplasma producing electrodes 10 and exposed to aGa plasma 23. External to quartz reaction tube 6, heater 7 is provided for the reaction tube to regulate the internal temperature of quartz reaction tube 6. - Using Ga vapor to obtain graphite film is an effective technique to obtain a single or multiple layers of large-area graphite film and is a practical technique directed to electronics device applications. To obtain a transparent, electrically conductive sheet or a similar, electrically conductive film having a large area and a low instance value, however, a process using Ga vapor must be performed a plurality of times to repeat a reaction until electrically conductive film as predetermined is obtained.
- As shown in
Fig. 12 , Ga vapor can be plasmatized and thus provided with energy to serve as a catalyst to graphitize amorphous carbon. When this is compared with using Ga vapor, the former can provide graphite film larger in thickness. Furthermore, using Ga plasma allows graphitization to be observed on a substrate having as low a temperature as approximately 400°C, and can thus induce graphitization at a lower temperature For use with a silicon device process, graphite film must be provided directly on a silicon device, and accordingly, it is essential to perform the process at low temperature. In this view, plasmatizing Ga vapor to allow graphite film to be provided in a process performed at low temperature is significantly effective for integration with the silicon device process. - Initially, a substrate to be processed, as aforementioned, is secured in quartz reaction tube 6 horizontally, and a turbo pump is used to vacuum the background to 10-6 Torr or lower.
-
Heater 12 for Ga is operated to facilitate evaporating liquid Ga 9, whileplasma producing electrodes 10 are used to plasmatize Ga vapor present at a location sandwiched between the electrodes, and heater 7 for the reaction tube is also used to heat the substrate exposed toGa plasma 11 to 400°C or higher andGa plasma 23 is brought into contact with a surface ofamorphous carbon film 21. To enhance the catalysis ofGa plasma 23, the substrate to be processed in contact withGa plasma 23 has a temperature more preferably of 800°C or higher. - The heat treatment in
Ga plasma 23 convertsamorphous carbon film 21 at least partially or entirely to graphite film. -
Fig. 13 is a schematic cross section of one example of a graphite film production apparatus employed in the present invention with a carbon source of a hydrocarbon gas. A fourth embodiment employs a graphite film production apparatus having quartz reaction tube 6 connected to a Ga vapor supply unit 15 and a hydrocarbongas supply unit 13. Ga vapor supply unit 15 receives liquid Ga 9, which is heated by a heater for Ga and thus evaporated to supply Ga vapor 5 to the interior of quartz reaction tube 6. Hydrocarbongas supply unit 13 receives hydxocarbon material serving as carbon material, such as camphor, phenanthrene, pyrene or the like, to supply a carbon source as hydrocarbon gas to the interior of quartz reaction tube 6. Quartz reaction tube 6 accommodates substrate 17 therein as a substrate to be processed - Quartz reaction tube 6 receives the hydrocarbon gas, which reacts with Ga vapor in a vicinity of substrate 17, therewhile the gas is decomposed and thus rapidly forms graphite film on substrate 17.
- When Ga is used to provide graphite film on a substrate, the Ga can disadvantageously be introduced into the film. When the substrate has a temperature of 600°C or higher, the Ga is hardly introduced into the film. When the substrate has a low temperature of 600°C or lower, and the Ga is accordingly introduced into the graphite film, annealing at approximately 500°C for a long period of time allows Ga to be separated and thus removed from the film.
- Initially, a substrate to be processed, as aforementioned, is secured in quartz reaction tube 6 horizontally, and a turbo pump is used to vacuum the background to 10-6 Torr or lower.
-
Heater 12 for Ga is operated to evaporate liquid Ga 9 to supply Ga vapor to the interior of quartz reaction tube 6. while avalve 16 located between hydrocarbongas supply unit 13 and quartz reaction tube 6 is opened to supply hydrocarbon gas. - Heater 7 for the reaction tube is operated to heat quartz reaction tube 6 to heat Ga vapor 5 therein to 400°C or higher and bring Ga vapor 5 into contact with a surface of
substrate 3. To enhance the catalysis of Ga vapor 5, Ga vapor 5 has a temperature more preferably of 800°C or higher. - The heat treatment in Ga vapor 5 provides graphite film on substrate 17.
- An arc process is employed to produce unpurified single-walled carbon nanotubes (CNTs), which are used to form an assembly portion provided as a 0.3 mm-diameter wire formed of stranded CNT filaments. The wire formed of stranded CNT filaments has a length of 10 mm.
- The wire formed of stranded CNT filaments is immersed for one hour in liquid gallium (Ga) heated to 600°C. In doing so, an ambient gas of Ar is used, set at a pressure of 1 × 10-5 Torr.
- Subsequently, the wire formed of stranded CNT filaments is drawn out of the liquid Ga and has Ga that adheres to its surface removed therefrom with diluted hydrochloric acid. The wire formed of stranded CNT filaments is thus provided with a graphite layer on a surface thereof, i.e., a carbon wire is obtained. The graphite layer has a thickness of approximately 5 µm.
- The carbon wire having the graphite layer is subjected to measurment of electrical resistance by a 4-terminal method.
- The carbon wire having the graphite layer has a value in electrical resistance decreased to approximately 1/5 of that of a sample of a comparative example 1 described later.
- An are process is employed to produce unpurified single-walled carbon nanotubes (CNTs), which are used to form an assembly portion provided as a 5 µm-diameter wire formed of stranded CNT filaments. The wire formed of stranded CNT filaments has a length of 10 mm.
- Then, phenanthrene (C14H10) is thermally decomposed to provide an amorphous carbon layer on a surface of the wire formed of stranded CNT filaments.
- Subsequently the wire formed of stranded CNT filaments is immersed for one hour in liquid gallium (Ga) heated to 600°C. In doing so, an ambient gas of Ar is used, set at a pressure of 2 atmospheres.
- Subsequently, the wire formed of stranded CNT filaments is drawn out of the liquid Ga and has Ga that adheres to its surface removed therefrom with diluted hydrochloric acid. The wire formed of stranded CNT filaments is thus provided with a graphite layer on a surface thereof, i.e., a carbon wire is obtained. The graphite layer has a thickness of approximately 1 µm.
- The carbon wire having the graphite layer is subjected to measurement of electrical resistance by a 4-terminal method.
-
- From this result, the carbon wire is considered to have an interior having a plurality of carbon nanotubes substantially integrated together.
- 10 nm-diameter, 300 µm long carbon nanotubes (CNTs) are prepared and overlapped by 100 µm to prepare an assembly portion implemented as a wire formed of bonded CNT filaments. The wire formed of bonded CNT filaments has a length of 50 mm and a diameter of 2 µm.
- Then, phenanthrene (C14H10) is thermally decomposed to provide an amorphous carbon layer on a surface of the wire formed of bonded CNT filaments.
- Subsequently the wire formed of bonded CNT filaments is immersed for one hour in liquid gallium (Ga) heated to 500°C. In doing so, an ambient gas of argon (Ar) is used, set at a pressure of 10 atmospheres is order to allow the wire to have its internal carbon nanotubes brought into close contact with one another.
- Subsquently, the wire formed of bonded CNT filaments is drawn out of the liquid Ga and has Ga that adheres to its surface removed therefrom with diluted hydrochloric acid. The wire formed of bonded CNT filaments is thus provided with a graphite layer on a surface thereof, i.e., a carbon wire is obtained. The graphite layer has a thickness of approximately 0.2 µm. Furthermore, it has been found that the graphite layer is formed in successive rings wrapping the internal CNTs and has thus become carbon nanotube (CNT).
- The carbon wire having the graphite layer is subjected to measurement of electrical resistance by a 4-terminal method.
- The carbon wire having the graphite layer has a value in electrical resistance smaller than the comparative example by one digit. This is probably because the carbon wire has an interior having carbon nanotubes in close contact with one another and thus integrated together.
- Catalytic CVD is employed to prepare a 30 nm-diameter, 500 µm long multiwalled carbon nanotube (CNT), and such CNTs are overlapped by 200 µm to form an assembly portion implemented as a wire formed of bonded CNT filaments. The wire formed of bonded CNT filaments has a length of 10 mm and a diamer of 0.6 µm
- Subsequently the wire formed of bonded CNT filaments is immersed for one hour in liquid gallium (Ga) heated to 550°C. More specifically, the liquid gallium and the wire formed of bonded CNT filaments are enclosed in a capsule of stainless steel. The capsule is surrounded by an ambient gas of argon (Ar). The ambient gas is compressed to exert pressure to the liquid gallium and the wire of bonded CNT filaments together with the capsule. The pressure is set at 100 atmospheres to allow the wire of bonded CNT filaments to have its internal carbon nanotubes brought into close contact with one another.
- Subsequently, the wire formed of bonded CNT filaments is drawn out of the liquid Ga and has Ga that adheres to its surface removed therefrom with diluted hydrochloric acid. The wire formed of bonded CNT filaments is thus provided with a graphite layer on a surface thereof, i.e., a carbon wire is obtained. The graphite layer has a thickness of approximately 80 nm. Furthermore, it has been found that the graphite layer is formed in successive rings wrapping the internal CNTs and has thus become carbon nanobube (CNT).
- Furthermore, such carbon wires each having the graphite layer are bundled and stranded together to provide a stranded wire to produce a 0.5 µm-diameter stranded wire, Then, as has been done in an above-described step, the stranded wire is immersed in liquid Ga to bond together a plurality of carbon wires configuring the stranded wire (i.e., a graphite layer is formed on a surface of a bundle of a plurality of carbon wires to surround the bundle). Thus the steps of bundling a plurality of carbon wires together; immersing the wire of the assembly of the bundled carbon wires in liquid Ga to bond the plurality of carbon wires together; and preparing and bundling together a plurality of such wires each of the assembly of the bonded carbon wires are repeated to produce a wire having a larger diameter (more specifically, a 0.1 mm-diameter wire formed of bonded wires).
- The carbon wire having the graphite layer is subjected to measurement of electrical resistance by a 4-terminal method.
- The carbon wire having the graphite layer has a value in electrical resistance smaller than the comparative example by two digits or larger. This is probably because the carbon wire has an interior having carbon nanotubes in close contact with one another and thus integrated together.
- An arc process is employed to produce unpurified, single-walled carbon nanotubes (CNTs) which are in turn used to form an assembly portion implemented as a 0.3 mm-diameter wire formed of stranded CNT filaments. The wire formed of stranded CNT filaments has a length of 10 mm.
- The wire formed of stranded CNT filaments is subjected to measurement of electrical resistance by a 4-terminal method.
- The comparative example's wire formed of stranded CNT filaments has a value in electrical resistance of 7.8 × 10-3 Ω•cm. This value is larger than that of copper by three digits or larger
- An arc process is employed to produce unpurified, single-walled carbon nanotubes (CNTs) which are in turn used to form an assembly portion implemented as a 0.3 mm-diameter wire formed of stranded CNT filaments. The wire formed of stranded CNT filaments has a length of 10 mm.
- The wire formed of stranded CNT filaments is immersed for one hour in liquid gallium (Ga) heated to 800°C. In doing so, an ambient gas of Ar is used, set at a pressure of 1 × 10-5 Torr.
- The wire of stranded CNT filaments immersed in the liquid Ga, as described above, has been decomposed in the liquid Ga and thus disappeared. Accordingly, it is preferable that the wire formed of stranded CNT filaments be immersed in liquid gallium heated to a temperature lower than 800°C, more preferably 750°C or lower.
- A ceramic substrate is prepared and thereon a slurry having CNTs dispersed therein is sprayed and then dried to form a CNT network on the substrate.
- For example 5 of the present invention and comparative example 3, an amorphous carbon film of approximately 5 nm on average is provided on the CNT network by laser abrasion.
- Subsequently, for examples 5, 6 of the present invention, the
Fig. 9 graphite film production apparatus is employed to produce graphite film. - A 1 m long 25 mm-diameter quartz tube is prepared as quartz reaction tube 6. Quartz reaction tube 6 accommodates an approximately 1 cm-diameter alumina container having liquid Ga 9 introduced therein, and in a vicinity thereof, substrate 17 bearing a plurality of
carbon nanotubes 2 forming a CNT network is placed as a substrate to be processed. - Initially, a substrate to be processed, as aforementioned, is secured in quartz reaction tube 6 horizontally, and a turbo pump is used to vacuum the background to 10-6 Torr or lower.
- Heater 7 for the reaction tube is operated to beat Ga vapor 5 to 650°C to perform a process for one hour and subsequently the reaction tube is slowly cooled again to room temperature. Note that comparative examples 3 and 4 are sample substrates which do not undergo the process with Ga vapor.
- The beat treatment with Ga vapor provides graphite film on a surface of the CNT networks For each example, the treatment's temperature and the processed substrate's sheet resistance value are as shown in table 1. Note that the sheet resistance value is measured in a 4-terminal method.
- Furthermore, for each example, on the electrically conductive sabstrate having the CNT network having a surface with the graphite film thereon, a resin sheet having thermosetting resin on a surface that is brought into contact with the CNT network is deposited from above, and then thermally set to transfer and secure the CNT network to the thermosetting resin to obtain a transparent, electrically conductive sheet, which has a sheet resistanee value as shown in table 1.
- A glass substrate is prepared and thereon a slurry having CNTs dispersed therein is sprayed and then dried to form a CNT network on the substrate. The substrate is washed with water and acetone to prevent a dispersant or a similar impurity from remaining on the CNT network.
- Subsequently, for example 7 of the present invention and comparative example 5, an organic gas (phenanthrene (C14H10)) is decomposed to provide amorphous carbon film on the CNT network.
- Subsequently, for examples 7, 8 of the present invention, the
Fig. 9 graphite film production apparatus is employed to produce graphite film. - A 1 m long, 25 mm-diameter quartz tube is prepared as quartz reaction tube 6. Quartz reaction tube 6 accommodates an approximately 1 cm-diameter alumina container having liquid Ga 9 introduced therein, and in a vicinity thereof, substrate 17 bearing a plurality of
carbon nanotubes 2 forming a CNT network is placed as a substrate to be processed. - Initially, a substrate to be processed, as aforementioned, is secured in quartz reaction tube 6 horizontally, and a turbo pump is used to vacuum the background to 10-6 Torr or lower.
- Heater 7 for the reaction tube is operated to heat Ga vapor 5 to 750°C to perform a process for 10 minutes and subsequently the reaction tube is slowly cooled again to room temperature. Note that comparative examples 5 and 6 are sample substrates which do not undergo the process with Ga vapor.
- The heat treatment with Ga vapor provides graphite film on a surface of the CNT network. For each example, the treatment's temperature and the processed substrate's sheet resistance value are as shown in table 2. Note that the sheet resistance value is measured in a 4-terminal method.
- Furthermore, for each example, on the electrically conductive substrate having the CNT network having a surface with the graphite film thereon, a resin sheet having thermosetting resin on a surface that is brought into contact with the CNT network is deposited from above, and then thermally set to transfer and secure the CNT network to the thermosetting resin to obtain a transparent, electrically conductive sheet, which has a sheet resistance value as shown in table 2.
Table 2 Examples Comparative Examples 7 8 5 6 Amorphous carbon film + - + - Ga vapor process + + - - Ga process temperature (°C) 750 750 - - Process time 10 min 10 min - - Transparent, electrically conductive sheet's sheet resistance value (kΩ/square) 5 10 300 800 - The
Fig. 10 graphite film production apparatus is employed to produce graphite film. - A 1 m long, 25 mm-diameter quartz tube is prepared as quartz reaction tube 6. Quartz reaction tube 6 accommodates an approximately 1 cm-diameter alumina container having liquid Ga introduced therein, and in a vicinity thereof, substrate 17 bearing
amorphous carbon film 21 is placed as a substrate to be processed. The substrate to be processed is a silicon substrate having a surface with an approximately
500 nm thick thermal oxide film thereon and an amorphous carbon film provided at that surface by laser abrasion. - Initially, a substrate to be processed, as aforementioned, is secured in quartz reaction tube 6 horizontally, and a turbo pump is used to vacuum the background to 10-6 Torr or lower.
- Heater 7 for the reaction tube is operated to heat Ga vapor 5 to a temperature indicated in table 3 to perform a process for one hour, and the reaction tube is slowly cooled again to room temperature.
- Examples 9-11 provide approximately 3-5 layers of graphite film on a surface of amorphous carbon film through the heat treatment in Ga vapor. Each sample substrate has a significantly smooth mirror surface without variation in color, or roughness.
- Subsequently, the aforementioned amorphous carbon deposition and Ga process are repeated until
substrate 3 has amorphous carbon film and graphite film thereon together forming a film having a thickness of approximately 50 nm. Each resultant sample substrate has a sheet resistance value, as shown in table 3. - In a comparative example 8, a substrate to be processed which is similar to those of the examples of the present invention is thermally treated in quartz reaction tube 6 at 600°C without liquid Ga 1 introduced therein. In other words, the substrate simply undergoes the heat treatment without subjecting amorphous carbon film to the Ga process. The other steps are performed similarly as done is the above examples of the present invention. The resultant sample substrate has a sheet resistance value as shown in table 3.
Table 3 Examples Comparative Examples 9 10 11 7 8 Process temperature (°C) 600 700 800 200 600 Sheet resistance value (kΩ/square) 100 20 6 ∞ 1500 - The
Fig. 11 graphite film production apparatus is employed to produce graphite film. - A 1 m long, 25 mm-diameter quartz tube is prepared as quartz reaction tube 6. Quartz reaction tube 6 accommodates subordinate
Ga reaction chamber 22 accommodating an approximately 1 cm-diameter alumina container having liquid Ga 9 introduced therein, and in a vicinity thereof, substrate 17 bearingamorphous carbon film 21 is placed as a substrate to be processed. The substrate to be processed is a silicon substrate having a surface with an approximately 500 nm thick thermal oxide film thereon and an amorphous carbon film provided at that surface by laser abrasion. - Initially, a substrate to be processed, as aforementioned, is secured in subordinate
Ga reaction chamber 22 horizontally, and a turbo pump is used to vacuum the background to 10-6 Torr or lower. - Heater 7 for the reaction tube is operated to heat Ga vapor 5 in subordinate
Ga reaction chamber 22 to a temperature indicated in table 4 to perform a process for 10 minutes, and the reaction tube is slowly cooled again to room temperature. - Examples 12-14 provide approximately 3-5 layers of graphite film on a surface of amorphous carbon film through the heat treatment in Ga vapor. Each sample substrate has a significantly smooth mirror surface without variation in color, or roughness.
- Subsequently, the aforementioned amorphous carbon deposition and Ga process are repeated until substrate 17 has amorphous carbon film and graphite film thereon together forming a film having a thickness of approximately 100 nm. For each example, the process's temperature and the resultant sample substrate's sheet resistance value are as shown in table 4.
- In a comparative example 10, a substrate to be processed which is similar to those of the examples of the present invention is thermally treated in quartz reaction tube 6 at 600°C for 10 minutes without liquid Ga 1 introduced therein. In other words, the substrate simply undergoes the heat treatment without subjecting amorphous carbon film to the Ga process. The other steps are performed similarly as done in the above examples of the present invention. The resultant sample substrate has a sheet resistance value as shown in table 4.
Table 4 Examples Comparative Examples 12 13 14 9 10 Process temperature (°C) 600 700 800 200 600 Sheet resistance value (kΩ/square) 120 30 5 ∞ 2000 - The
Fig. 12 graphite film production apparatus is employed to produce graphite film. - A 1 m long, 25 mm-diameter quartz tube is prepared as quartz reaction tube 6. Quartz reaction tube 6 accommodates a pair of
plasma producing electrodes 10 therein, and in a vicinity thereof,alumina container 20 having a diameter of approximately 1 cm and having liquid Ga 1 introduced therein is placed. At the alumina container,heater 12 is placed for Ga. Substrate 17 bearingamorphous carbon film 21 thereof is placed betweenplasma producing electrodes 10 as a substrate to be processed. The substrate to be processed is a silicon substrate having a surface with an approximately 500 nm thick thermal oxide film thereon and an amorphous carbon film provided at that surface by laser abrasion. - Initially, a substrate to be processed, as aforementioned, is secured between
plasma producing electrodes 10 horizontally, and a turbo pump is used to vacuum the background to 10-6 Torr or lower. -
Heater 12 for Ga is operated to facilitate evaporating liquid Ga 9, whileplasma producing electrodes 10 are used to plasmatize Ga vapor present at a location sandwiched between the electrodes, and heater 7 for the reaction tube is also used to heat the substrate in contact withGa plasma 23 to a temperature indicated in table 5 and a 10-minute process is also performed, and the reaction tube is slowly cooled again to room temperature. - Examples 15-17 each provide approximately 3-5 layers of graphite film on a surface of the substrate through the heat treatment in Ga plasma. Each sample substrate has a significantly smooth mirror surface without variation in color, or roughness.
- Subsequently, the aforementioned amorphous carbon deposition and Ga process are repeated until substrate 17 has amorphous carbon film and graphite film thereon together forming a film having a thickness of approximately 100 nm. For each example, the process's temperature and the resultant sample substrate's sheet resistance value are as shown in table 5.
- In a comparative example 12, a substrate to be processed which is similar to those of the examples of the present invention is thermally treated in quartz reaction tubs 6 at 600°C for 10 minutes without liquid Ga 9 introduced therein. In other words, the substrate simply undergoes the heat treatment without subjecting amorphous carbon
film to the Ga process. The other steps are performed similarly as done in the above examples of the present invention. The resultant sample substrate has a sheet resistance value as shown in table 5.Table 5 Examples Comparative Examples 15 16 17 11 12 Process temperature (°C) 400 600 800 200 600 Sheet resistance value (kΩ/square) 90 60 3 ∞ 2200 - The
Fig. 13 graphite film production apparatus is employed to produce graphite film. - A 1 m long, 25 mm-diameter quartz tube is prepared as quartz reaction tube 6. Quartz reaction tube 6 is connected to Ga vapor supply unit 15 and hydrocarbon
gas supply unit 13. Ga vapor supply unit 15 has liquid Ga introduced therein. Hydrocarbongas supply unit 13 has phenanthrene introduced therein as a carbon source material. As a substrate to be processed, substrate 17 is placed in quartz reaction tube 6. - Initially, a substrate to be processed, as aforementioned, is secured in quartz reaction tube 6 horizontally, and a turbo pump is used to vacuum the background to 10-6 Torr or lower.
-
Heater 12 for Ga is used to evaporate liquid Ga 9 to supply Ga vapor to the interior of quartz reaction tube 6, whilevalve 16 located between hydrocarbongas supply unit 13 having phenanthrene introduced therein and quartz reaction tube 6 is opened to supply hydrocarbon gas. - Heater 7 for the reaction tube is operated to raise the temperature in quartz reaction tube 6 to that indicated in table 6 and a 30-minute process is performed, and the reaction tube is slowly cooled again to room temperature.
- Examples 18-20 each provide graphite film on a surface of the substrate through the heat treatment in Ga vapor to have a thickness of 200 nm. Each sample substrate has a significantly smooth mirror surface without variation in color, or roughness. For each example, the process's temperature and the resultant sample substrate's sheet resistance value are as shown in table 6.
- In a comparative example 14, a substrate to be processed which is similar to those of the examples of the present invention is thermally treated in quartz reaction tube 6 at 600°C for 30 minutes without liquid Ga 9 introduced therein. In other words, the substrate simply undergoes the heat treatment without subjecting amorphous carbon film to the Ga process. The other steps are performed similarly as done in the above examples of the present invention. The resultant sample substrate has a sheet resistance value as shown in table 6.
Table 6 Examples Comparative Examples 18 19 20 13 14 Process temperature (°C) 400 600 800 200 600 Sheet resistance value (kΩ/square) 160 40 2 ∞ 1500 - The present invention is advantageously applicable particularly to carbon wires configured of a plurality of short carbon nanotubes combined together, and wire assemblies employing such carbon wires.
- Furthermore, the present invention allows mass production of a significantly thin stack of graphite layers or a monolayer of graphite film in large areas. The monolayer of graphite film having a large area can be used to allow application to an LSI or similar, large scale graphene integrated circuit. Furthermore, increasing thickness allows a transparent, electrically conductive sheet having a large area to be formed, and it is expected to be applied to a large size liquid crystal display.
- 1: carbon wire, 2: carbon nanotube, 3: assembly portion 4: graphite layer, 5: wire assembly, 6: quarts reaction tube, 7: heater for reaction tube, 8: evacuation system, 9: liquid Ga, 10: plasma producing electrode, 11: amorphous carbon layer, 12: heater for Ga, 13: hydrocarbon gas supply unit, 14: reactor, 15: Ga vapor supply unit, 16: valve, 17: substrate, 18: carbon nanotube network, 19: sheet of resin, 20: alumina container, 21: amorphous carbon film 22: subordinate Ga reaction chamber, 23: Ga plasma, 24: Ga vapor.
Claims (18)
- A method of producing carbon wire 1, comprising the steps of:preparing an assembly portion 3 formed of a plurality of carbon filaments in contact with one another; andexposing a surface of said assembly portion 3 to liquid gallium 9 to provide a graphite layer 4 on the surface of said assembly portion 3.
- The method of producing carbon wire 1 according to claim 1, wherein in the step of exposing, compressive stress is exerted to said assembly portion 3.
- The method of producing carbon wire 1 according to claim 2, wherein in the step of exposing, said liquid gallium is compressed to exert compressive stress to said assembly portion 3.
- The method of producing carbon wire 1 according to claim 3, wherein in the step of exposing, said liquid gallium is exposed to an ambient gas regulated in pressure to compress said liquid gallium.
- The method of producing carbon wire 1 according to claim 1, wherein in the step of exposing, said liquid gallium has a temperature ranging from 450°C to 750°C.
- The method of producing carbon wire 1 according to claim 1, comprising, before the step of exposing, the step of providing an amorphous carbon layer 11 as a surface layer of said assembly portion 3.
- The method of producing carbon wire 1 according to claim 1, further comprising, after the step of exposing, the step of removing gallium adhering to a surface of said carbon wire 1.
- A method of producing a wire assembly 5, comprising the steps of:producing a plurality of carbon wires 1 in the method of producing carbon wire 1 according to any one of claims 1-7; andstranding said plurality of carbon wires 1 together to form a wire assembly 5.
- A method of producing electrically conductive film having a carbon nanotube network 18 formed of a plurality of carbon nanotubes 2 linked together by graphite film, comprising the step of exposing a carbon nanotube network 18 to Ga (gallium) vapor to provide said graphite film.
- A method of producing electrically conductive film according to claim 9, comprising the steps of:providing amorphous carbon film 21 on said carbon nanotube 18 prior to said step of exposing,wherein in said step of exposing, said carbon nanotube network 18 and said amorphous carbon film 21 obtained in the step of providing are exposed to said Ga vapor to provide said graphite film.
- The method of producing the electrically conductive film according to claim 9, comprising, before the step of exposing, the step of mechanically pressure-welding those portions of plurality of carbon nanotubes 2 forming said carbon nanotube network 18 which are in contact with one another.
- A method of producing an electrically conductive substrate formed with a substrate and an electrically conductive film provided on said substrate and having a carbon nanotube network 18 formed of a plurality of carbon nanotubes 2 linked together by graphite film, comprising the steps of:forming a carbon nanotube network 18 on a substrate; andexposing said carbon nanotube network 18 to Ga vapor to provide said graphite film.
- A method of producing an electrically conductive substrate according to claim 12, comprising the steps of:providing amorphous carbon film 21 on said carbon nanotube network 18 prior to the step of exposing,wherein in said step of exposing, said carbon nanotube network 18 and said amorphous carbon film 21 that is obtained in the step of providing are exposed to Ga vapor to provide said graphite film.
- The method of producing an electrically conductive substrate according to claim 12, comprising, before the step of exposing, the step of mechanically pressure-welding those portions of a plurality of carbon nanotubes 2 forming said carbon nanotube network 18 which are in contact with one another.
- A method of producing the transparent, electrically conductive sheet formed with a sheet of resin 19 and an and having a carbon nanotube network 18 formed of a plurality of carbon nanotubes 2 linked together by graphite film, the method comprising steps of:forming a carbon nanotube network 18 on a substrate 17;exposing said carbon nanotube network 18 to Ga vapor to provide said graphite film; andtransferring to a sheet of resin 19 an electrically conductive film having said carbon nanotube 18 formed of a plurality of carbon nanotubes 2 linked together by graphite film in the step of exposing.
- A method of producing the transparent, electrically conductive sheet according to claim 15, the method comprising the steps of:providing amorphous carbon film 21 on said carbon nanotube network 18 prior to the step of exposing,wherein in said step of exposing, said carbon nanotube network 18 and said amorphous carbon film 21 that is obtained in the step of providing are exposed to Ga vapor to provide said graphite film.
- The method of producing the transparent, electrically conductive sheet according to claim 15, comprising, before the step of exposing, the step of mechanically pressure-welding those portions of said plurality of carbon nanotubes 2 forming said carbon nanotube network 18 which are in contact with one another.
- The method of producing the transparent, electrically conductive sheet according to any one of claims 15 and 16, wherein the step of transferring transfers said electrically that is formed of one of thermosetting resin and ultraviolet curable resin, the method further comprising the step of setting/curing one of said thermosetting resin and said ultraviolet curable resin.
Applications Claiming Priority (4)
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JP2008129637A JP2009274936A (en) | 2008-05-16 | 2008-05-16 | Carbon wire, assembled wire material and method for manufacturing those |
JP2008200869A JP5578639B2 (en) | 2008-08-04 | 2008-08-04 | Graphite film manufacturing method |
JP2008218314A JP5578640B2 (en) | 2008-08-27 | 2008-08-27 | Conductive film, conductive substrate, transparent conductive film, and production method thereof |
PCT/JP2009/058681 WO2009139331A1 (en) | 2008-05-16 | 2009-05-08 | Carbon wire, nanostructure composed of carbon film, method for producing the carbon wire, and method for producing nanostructure |
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EP2298697A1 EP2298697A1 (en) | 2011-03-23 |
EP2298697A4 EP2298697A4 (en) | 2013-01-23 |
EP2298697B1 true EP2298697B1 (en) | 2019-02-13 |
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EP09746538.9A Not-in-force EP2298697B1 (en) | 2008-05-16 | 2009-05-08 | Method for producing a carbon wire assembly and a conductive film |
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US (2) | US8668952B2 (en) |
EP (1) | EP2298697B1 (en) |
KR (1) | KR20110021721A (en) |
CN (1) | CN102026918B (en) |
WO (1) | WO2009139331A1 (en) |
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JP5463566B2 (en) * | 2009-06-02 | 2014-04-09 | 住友電気工業株式会社 | Molded body and method for producing the same |
US9281385B2 (en) * | 2010-06-18 | 2016-03-08 | Samsung Electronics Co., Ltd. | Semiconducting graphene composition, and electrical device including the same |
KR101312701B1 (en) * | 2011-05-23 | 2013-10-01 | 국립대학법인 울산과학기술대학교 산학협력단 | Method of preparing gallium nanofluid, gallium nanofluid prepared by the same, and coolant of fast reactor including gallium nanofluid |
US9177688B2 (en) | 2011-11-22 | 2015-11-03 | International Business Machines Corporation | Carbon nanotube-graphene hybrid transparent conductor and field effect transistor |
JP6105204B2 (en) * | 2012-02-10 | 2017-03-29 | 株式会社日立ハイテクサイエンス | Sample preparation method for TEM observation |
US9574990B2 (en) * | 2012-02-28 | 2017-02-21 | Hewlett-Packard Development Company, L.P. | SERS structures with nanoporous materials |
JP5927522B2 (en) * | 2012-03-16 | 2016-06-01 | 日本電気株式会社 | Carbon material structural material manufacturing method and carbon material structural material |
CN103050798B (en) * | 2012-12-13 | 2015-02-04 | 中国电力科学研究院 | Graphene nanomaterial wire splicing fitting and splicing method |
JP6179587B2 (en) | 2013-02-22 | 2017-08-16 | 住友電気工業株式会社 | Porous member and catalyst member |
FR3007189B1 (en) | 2013-06-17 | 2015-05-22 | Nexans | METHOD FOR MANUFACTURING AN ELECTRICALLY CONDUCTIVE ELEMENT |
CN105329873B (en) * | 2014-07-08 | 2018-02-27 | 清华大学 | CNT sponge and preparation method thereof |
CN105439114B (en) * | 2014-07-25 | 2018-02-27 | 清华大学 | Carbon-fiber film and preparation method thereof |
CN106661255A (en) | 2014-08-07 | 2017-05-10 | 沙特基础工业全球技术有限公司 | Conductive multilayer sheet for thermal forming applications |
JP6810343B2 (en) * | 2016-10-17 | 2021-01-06 | 富士通株式会社 | Manufacturing method of carbon nanotube structure, heat dissipation sheet and carbon nanotube structure |
CN110368972B (en) * | 2019-08-09 | 2022-01-28 | 陕西科技大学 | Core-shell SiC @ C catalyst for microwave-assisted catalytic depolymerization of solid waste and preparation method thereof |
CN110368971B (en) * | 2019-08-09 | 2022-01-28 | 陕西科技大学 | SiC-based composite catalyst for microwave-assisted depolymerization of solid waste and preparation method thereof |
CN113562690B (en) * | 2020-04-28 | 2022-05-31 | 清华大学 | Nano manipulator |
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- 2009-05-08 US US12/920,760 patent/US8668952B2/en not_active Expired - Fee Related
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US20130224518A1 (en) | 2013-08-29 |
EP2298697A1 (en) | 2011-03-23 |
EP2298697A4 (en) | 2013-01-23 |
WO2009139331A1 (en) | 2009-11-19 |
US20110003174A1 (en) | 2011-01-06 |
CN102026918B (en) | 2014-08-27 |
KR20110021721A (en) | 2011-03-04 |
US8668952B2 (en) | 2014-03-11 |
WO2009139331A9 (en) | 2010-02-18 |
CN102026918A (en) | 2011-04-20 |
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